1 /*
   2  * Copyright (c) 1997, 2020, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/systemDictionary.hpp"
  27 #include "gc/shared/barrierSet.hpp"
  28 #include "gc/shared/c2/barrierSetC2.hpp"
  29 #include "memory/allocation.inline.hpp"
  30 #include "memory/resourceArea.hpp"
  31 #include "oops/objArrayKlass.hpp"
  32 #include "opto/addnode.hpp"
  33 #include "opto/castnode.hpp"
  34 #include "opto/cfgnode.hpp"
  35 #include "opto/connode.hpp"
  36 #include "opto/convertnode.hpp"
  37 #include "opto/loopnode.hpp"
  38 #include "opto/machnode.hpp"
  39 #include "opto/movenode.hpp"
  40 #include "opto/narrowptrnode.hpp"
  41 #include "opto/mulnode.hpp"
  42 #include "opto/phaseX.hpp"
  43 #include "opto/regmask.hpp"
  44 #include "opto/runtime.hpp"
  45 #include "opto/subnode.hpp"
  46 #include "utilities/vmError.hpp"
  47 
  48 // Portions of code courtesy of Clifford Click
  49 
  50 // Optimization - Graph Style
  51 
  52 //=============================================================================
  53 //------------------------------Value------------------------------------------
  54 // Compute the type of the RegionNode.
  55 const Type* RegionNode::Value(PhaseGVN* phase) const {
  56   for( uint i=1; i<req(); ++i ) {       // For all paths in
  57     Node *n = in(i);            // Get Control source
  58     if( !n ) continue;          // Missing inputs are TOP
  59     if( phase->type(n) == Type::CONTROL )
  60       return Type::CONTROL;
  61   }
  62   return Type::TOP;             // All paths dead?  Then so are we
  63 }
  64 
  65 //------------------------------Identity---------------------------------------
  66 // Check for Region being Identity.
  67 Node* RegionNode::Identity(PhaseGVN* phase) {
  68   // Cannot have Region be an identity, even if it has only 1 input.
  69   // Phi users cannot have their Region input folded away for them,
  70   // since they need to select the proper data input
  71   return this;
  72 }
  73 
  74 //------------------------------merge_region-----------------------------------
  75 // If a Region flows into a Region, merge into one big happy merge.  This is
  76 // hard to do if there is stuff that has to happen
  77 static Node *merge_region(RegionNode *region, PhaseGVN *phase) {
  78   if( region->Opcode() != Op_Region ) // Do not do to LoopNodes
  79     return NULL;
  80   Node *progress = NULL;        // Progress flag
  81   PhaseIterGVN *igvn = phase->is_IterGVN();
  82 
  83   uint rreq = region->req();
  84   for( uint i = 1; i < rreq; i++ ) {
  85     Node *r = region->in(i);
  86     if( r && r->Opcode() == Op_Region && // Found a region?
  87         r->in(0) == r &&        // Not already collapsed?
  88         r != region &&          // Avoid stupid situations
  89         r->outcnt() == 2 ) {    // Self user and 'region' user only?
  90       assert(!r->as_Region()->has_phi(), "no phi users");
  91       if( !progress ) {         // No progress
  92         if (region->has_phi()) {
  93           return NULL;        // Only flatten if no Phi users
  94           // igvn->hash_delete( phi );
  95         }
  96         igvn->hash_delete( region );
  97         progress = region;      // Making progress
  98       }
  99       igvn->hash_delete( r );
 100 
 101       // Append inputs to 'r' onto 'region'
 102       for( uint j = 1; j < r->req(); j++ ) {
 103         // Move an input from 'r' to 'region'
 104         region->add_req(r->in(j));
 105         r->set_req(j, phase->C->top());
 106         // Update phis of 'region'
 107         //for( uint k = 0; k < max; k++ ) {
 108         //  Node *phi = region->out(k);
 109         //  if( phi->is_Phi() ) {
 110         //    phi->add_req(phi->in(i));
 111         //  }
 112         //}
 113 
 114         rreq++;                 // One more input to Region
 115       } // Found a region to merge into Region
 116       igvn->_worklist.push(r);
 117       // Clobber pointer to the now dead 'r'
 118       region->set_req(i, phase->C->top());
 119     }
 120   }
 121 
 122   return progress;
 123 }
 124 
 125 
 126 
 127 //--------------------------------has_phi--------------------------------------
 128 // Helper function: Return any PhiNode that uses this region or NULL
 129 PhiNode* RegionNode::has_phi() const {
 130   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 131     Node* phi = fast_out(i);
 132     if (phi->is_Phi()) {   // Check for Phi users
 133       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 134       return phi->as_Phi();  // this one is good enough
 135     }
 136   }
 137 
 138   return NULL;
 139 }
 140 
 141 
 142 //-----------------------------has_unique_phi----------------------------------
 143 // Helper function: Return the only PhiNode that uses this region or NULL
 144 PhiNode* RegionNode::has_unique_phi() const {
 145   // Check that only one use is a Phi
 146   PhiNode* only_phi = NULL;
 147   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 148     Node* phi = fast_out(i);
 149     if (phi->is_Phi()) {   // Check for Phi users
 150       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 151       if (only_phi == NULL) {
 152         only_phi = phi->as_Phi();
 153       } else {
 154         return NULL;  // multiple phis
 155       }
 156     }
 157   }
 158 
 159   return only_phi;
 160 }
 161 
 162 
 163 //------------------------------check_phi_clipping-----------------------------
 164 // Helper function for RegionNode's identification of FP clipping
 165 // Check inputs to the Phi
 166 static bool check_phi_clipping( PhiNode *phi, ConNode * &min, uint &min_idx, ConNode * &max, uint &max_idx, Node * &val, uint &val_idx ) {
 167   min     = NULL;
 168   max     = NULL;
 169   val     = NULL;
 170   min_idx = 0;
 171   max_idx = 0;
 172   val_idx = 0;
 173   uint  phi_max = phi->req();
 174   if( phi_max == 4 ) {
 175     for( uint j = 1; j < phi_max; ++j ) {
 176       Node *n = phi->in(j);
 177       int opcode = n->Opcode();
 178       switch( opcode ) {
 179       case Op_ConI:
 180         {
 181           if( min == NULL ) {
 182             min     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 183             min_idx = j;
 184           } else {
 185             max     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 186             max_idx = j;
 187             if( min->get_int() > max->get_int() ) {
 188               // Swap min and max
 189               ConNode *temp;
 190               uint     temp_idx;
 191               temp     = min;     min     = max;     max     = temp;
 192               temp_idx = min_idx; min_idx = max_idx; max_idx = temp_idx;
 193             }
 194           }
 195         }
 196         break;
 197       default:
 198         {
 199           val = n;
 200           val_idx = j;
 201         }
 202         break;
 203       }
 204     }
 205   }
 206   return ( min && max && val && (min->get_int() <= 0) && (max->get_int() >=0) );
 207 }
 208 
 209 
 210 //------------------------------check_if_clipping------------------------------
 211 // Helper function for RegionNode's identification of FP clipping
 212 // Check that inputs to Region come from two IfNodes,
 213 //
 214 //            If
 215 //      False    True
 216 //       If        |
 217 //  False  True    |
 218 //    |      |     |
 219 //  RegionNode_inputs
 220 //
 221 static bool check_if_clipping( const RegionNode *region, IfNode * &bot_if, IfNode * &top_if ) {
 222   top_if = NULL;
 223   bot_if = NULL;
 224 
 225   // Check control structure above RegionNode for (if  ( if  ) )
 226   Node *in1 = region->in(1);
 227   Node *in2 = region->in(2);
 228   Node *in3 = region->in(3);
 229   // Check that all inputs are projections
 230   if( in1->is_Proj() && in2->is_Proj() && in3->is_Proj() ) {
 231     Node *in10 = in1->in(0);
 232     Node *in20 = in2->in(0);
 233     Node *in30 = in3->in(0);
 234     // Check that #1 and #2 are ifTrue and ifFalse from same If
 235     if( in10 != NULL && in10->is_If() &&
 236         in20 != NULL && in20->is_If() &&
 237         in30 != NULL && in30->is_If() && in10 == in20 &&
 238         (in1->Opcode() != in2->Opcode()) ) {
 239       Node  *in100 = in10->in(0);
 240       Node *in1000 = (in100 != NULL && in100->is_Proj()) ? in100->in(0) : NULL;
 241       // Check that control for in10 comes from other branch of IF from in3
 242       if( in1000 != NULL && in1000->is_If() &&
 243           in30 == in1000 && (in3->Opcode() != in100->Opcode()) ) {
 244         // Control pattern checks
 245         top_if = (IfNode*)in1000;
 246         bot_if = (IfNode*)in10;
 247       }
 248     }
 249   }
 250 
 251   return (top_if != NULL);
 252 }
 253 
 254 
 255 //------------------------------check_convf2i_clipping-------------------------
 256 // Helper function for RegionNode's identification of FP clipping
 257 // Verify that the value input to the phi comes from "ConvF2I; LShift; RShift"
 258 static bool check_convf2i_clipping( PhiNode *phi, uint idx, ConvF2INode * &convf2i, Node *min, Node *max) {
 259   convf2i = NULL;
 260 
 261   // Check for the RShiftNode
 262   Node *rshift = phi->in(idx);
 263   assert( rshift, "Previous checks ensure phi input is present");
 264   if( rshift->Opcode() != Op_RShiftI )  { return false; }
 265 
 266   // Check for the LShiftNode
 267   Node *lshift = rshift->in(1);
 268   assert( lshift, "Previous checks ensure phi input is present");
 269   if( lshift->Opcode() != Op_LShiftI )  { return false; }
 270 
 271   // Check for the ConvF2INode
 272   Node *conv = lshift->in(1);
 273   if( conv->Opcode() != Op_ConvF2I ) { return false; }
 274 
 275   // Check that shift amounts are only to get sign bits set after F2I
 276   jint max_cutoff     = max->get_int();
 277   jint min_cutoff     = min->get_int();
 278   jint left_shift     = lshift->in(2)->get_int();
 279   jint right_shift    = rshift->in(2)->get_int();
 280   jint max_post_shift = nth_bit(BitsPerJavaInteger - left_shift - 1);
 281   if( left_shift != right_shift ||
 282       0 > left_shift || left_shift >= BitsPerJavaInteger ||
 283       max_post_shift < max_cutoff ||
 284       max_post_shift < -min_cutoff ) {
 285     // Shifts are necessary but current transformation eliminates them
 286     return false;
 287   }
 288 
 289   // OK to return the result of ConvF2I without shifting
 290   convf2i = (ConvF2INode*)conv;
 291   return true;
 292 }
 293 
 294 
 295 //------------------------------check_compare_clipping-------------------------
 296 // Helper function for RegionNode's identification of FP clipping
 297 static bool check_compare_clipping( bool less_than, IfNode *iff, ConNode *limit, Node * & input ) {
 298   Node *i1 = iff->in(1);
 299   if ( !i1->is_Bool() ) { return false; }
 300   BoolNode *bool1 = i1->as_Bool();
 301   if(       less_than && bool1->_test._test != BoolTest::le ) { return false; }
 302   else if( !less_than && bool1->_test._test != BoolTest::lt ) { return false; }
 303   const Node *cmpF = bool1->in(1);
 304   if( cmpF->Opcode() != Op_CmpF )      { return false; }
 305   // Test that the float value being compared against
 306   // is equivalent to the int value used as a limit
 307   Node *nodef = cmpF->in(2);
 308   if( nodef->Opcode() != Op_ConF ) { return false; }
 309   jfloat conf = nodef->getf();
 310   jint   coni = limit->get_int();
 311   if( ((int)conf) != coni )        { return false; }
 312   input = cmpF->in(1);
 313   return true;
 314 }
 315 
 316 //------------------------------is_unreachable_region--------------------------
 317 // Find if the Region node is reachable from the root.
 318 bool RegionNode::is_unreachable_region(PhaseGVN *phase) const {
 319   assert(req() == 2, "");
 320 
 321   // First, cut the simple case of fallthrough region when NONE of
 322   // region's phis references itself directly or through a data node.
 323   uint max = outcnt();
 324   uint i;
 325   for (i = 0; i < max; i++) {
 326     Node* phi = raw_out(i);
 327     if (phi != NULL && phi->is_Phi()) {
 328       assert(phase->eqv(phi->in(0), this) && phi->req() == 2, "");
 329       if (phi->outcnt() == 0)
 330         continue; // Safe case - no loops
 331       if (phi->outcnt() == 1) {
 332         Node* u = phi->raw_out(0);
 333         // Skip if only one use is an other Phi or Call or Uncommon trap.
 334         // It is safe to consider this case as fallthrough.
 335         if (u != NULL && (u->is_Phi() || u->is_CFG()))
 336           continue;
 337       }
 338       // Check when phi references itself directly or through an other node.
 339       if (phi->as_Phi()->simple_data_loop_check(phi->in(1)) >= PhiNode::Unsafe)
 340         break; // Found possible unsafe data loop.
 341     }
 342   }
 343   if (i >= max)
 344     return false; // An unsafe case was NOT found - don't need graph walk.
 345 
 346   // Unsafe case - check if the Region node is reachable from root.
 347   ResourceMark rm;
 348 
 349   Node_List nstack;
 350   VectorSet visited;
 351 
 352   // Mark all control nodes reachable from root outputs
 353   Node *n = (Node*)phase->C->root();
 354   nstack.push(n);
 355   visited.set(n->_idx);
 356   while (nstack.size() != 0) {
 357     n = nstack.pop();
 358     uint max = n->outcnt();
 359     for (uint i = 0; i < max; i++) {
 360       Node* m = n->raw_out(i);
 361       if (m != NULL && m->is_CFG()) {
 362         if (phase->eqv(m, this)) {
 363           return false; // We reached the Region node - it is not dead.
 364         }
 365         if (!visited.test_set(m->_idx))
 366           nstack.push(m);
 367       }
 368     }
 369   }
 370 
 371   return true; // The Region node is unreachable - it is dead.
 372 }
 373 
 374 bool RegionNode::try_clean_mem_phi(PhaseGVN *phase) {
 375   // Incremental inlining + PhaseStringOpts sometimes produce:
 376   //
 377   // cmpP with 1 top input
 378   //           |
 379   //          If
 380   //         /  \
 381   //   IfFalse  IfTrue  /- Some Node
 382   //         \  /      /    /
 383   //        Region    / /-MergeMem
 384   //             \---Phi
 385   //
 386   //
 387   // It's expected by PhaseStringOpts that the Region goes away and is
 388   // replaced by If's control input but because there's still a Phi,
 389   // the Region stays in the graph. The top input from the cmpP is
 390   // propagated forward and a subgraph that is useful goes away. The
 391   // code below replaces the Phi with the MergeMem so that the Region
 392   // is simplified.
 393 
 394   PhiNode* phi = has_unique_phi();
 395   if (phi && phi->type() == Type::MEMORY && req() == 3 && phi->is_diamond_phi(true)) {
 396     MergeMemNode* m = NULL;
 397     assert(phi->req() == 3, "same as region");
 398     for (uint i = 1; i < 3; ++i) {
 399       Node *mem = phi->in(i);
 400       if (mem && mem->is_MergeMem() && in(i)->outcnt() == 1) {
 401         // Nothing is control-dependent on path #i except the region itself.
 402         m = mem->as_MergeMem();
 403         uint j = 3 - i;
 404         Node* other = phi->in(j);
 405         if (other && other == m->base_memory()) {
 406           // m is a successor memory to other, and is not pinned inside the diamond, so push it out.
 407           // This will allow the diamond to collapse completely.
 408           phase->is_IterGVN()->replace_node(phi, m);
 409           return true;
 410         }
 411       }
 412     }
 413   }
 414   return false;
 415 }
 416 
 417 //------------------------------Ideal------------------------------------------
 418 // Return a node which is more "ideal" than the current node.  Must preserve
 419 // the CFG, but we can still strip out dead paths.
 420 Node *RegionNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 421   if( !can_reshape && !in(0) ) return NULL;     // Already degraded to a Copy
 422   assert(!in(0) || !in(0)->is_Root(), "not a specially hidden merge");
 423 
 424   // Check for RegionNode with no Phi users and both inputs come from either
 425   // arm of the same IF.  If found, then the control-flow split is useless.
 426   bool has_phis = false;
 427   if (can_reshape) {            // Need DU info to check for Phi users
 428     has_phis = (has_phi() != NULL);       // Cache result
 429     if (has_phis && try_clean_mem_phi(phase)) {
 430       has_phis = false;
 431     }
 432 
 433     if (!has_phis) {            // No Phi users?  Nothing merging?
 434       for (uint i = 1; i < req()-1; i++) {
 435         Node *if1 = in(i);
 436         if( !if1 ) continue;
 437         Node *iff = if1->in(0);
 438         if( !iff || !iff->is_If() ) continue;
 439         for( uint j=i+1; j<req(); j++ ) {
 440           if( in(j) && in(j)->in(0) == iff &&
 441               if1->Opcode() != in(j)->Opcode() ) {
 442             // Add the IF Projections to the worklist. They (and the IF itself)
 443             // will be eliminated if dead.
 444             phase->is_IterGVN()->add_users_to_worklist(iff);
 445             set_req(i, iff->in(0));// Skip around the useless IF diamond
 446             set_req(j, NULL);
 447             return this;      // Record progress
 448           }
 449         }
 450       }
 451     }
 452   }
 453 
 454   // Remove TOP or NULL input paths. If only 1 input path remains, this Region
 455   // degrades to a copy.
 456   bool add_to_worklist = false;
 457   bool modified = false;
 458   int cnt = 0;                  // Count of values merging
 459   DEBUG_ONLY( int cnt_orig = req(); ) // Save original inputs count
 460   int del_it = 0;               // The last input path we delete
 461   // For all inputs...
 462   for( uint i=1; i<req(); ++i ){// For all paths in
 463     Node *n = in(i);            // Get the input
 464     if( n != NULL ) {
 465       // Remove useless control copy inputs
 466       if( n->is_Region() && n->as_Region()->is_copy() ) {
 467         set_req(i, n->nonnull_req());
 468         modified = true;
 469         i--;
 470         continue;
 471       }
 472       if( n->is_Proj() ) {      // Remove useless rethrows
 473         Node *call = n->in(0);
 474         if (call->is_Call() && call->as_Call()->entry_point() == OptoRuntime::rethrow_stub()) {
 475           set_req(i, call->in(0));
 476           modified = true;
 477           i--;
 478           continue;
 479         }
 480       }
 481       if( phase->type(n) == Type::TOP ) {
 482         set_req(i, NULL);       // Ignore TOP inputs
 483         modified = true;
 484         i--;
 485         continue;
 486       }
 487       cnt++;                    // One more value merging
 488 
 489     } else if (can_reshape) {   // Else found dead path with DU info
 490       PhaseIterGVN *igvn = phase->is_IterGVN();
 491       del_req(i);               // Yank path from self
 492       del_it = i;
 493       uint max = outcnt();
 494       DUIterator j;
 495       bool progress = true;
 496       while(progress) {         // Need to establish property over all users
 497         progress = false;
 498         for (j = outs(); has_out(j); j++) {
 499           Node *n = out(j);
 500           if( n->req() != req() && n->is_Phi() ) {
 501             assert( n->in(0) == this, "" );
 502             igvn->hash_delete(n); // Yank from hash before hacking edges
 503             n->set_req_X(i,NULL,igvn);// Correct DU info
 504             n->del_req(i);        // Yank path from Phis
 505             if( max != outcnt() ) {
 506               progress = true;
 507               j = refresh_out_pos(j);
 508               max = outcnt();
 509             }
 510           }
 511         }
 512       }
 513       add_to_worklist = true;
 514       i--;
 515     }
 516   }
 517 
 518   if (can_reshape && cnt == 1) {
 519     // Is it dead loop?
 520     // If it is LoopNopde it had 2 (+1 itself) inputs and
 521     // one of them was cut. The loop is dead if it was EntryContol.
 522     // Loop node may have only one input because entry path
 523     // is removed in PhaseIdealLoop::Dominators().
 524     assert(!this->is_Loop() || cnt_orig <= 3, "Loop node should have 3 or less inputs");
 525     if ((this->is_Loop() && (del_it == LoopNode::EntryControl ||
 526                              (del_it == 0 && is_unreachable_region(phase)))) ||
 527         (!this->is_Loop() && has_phis && is_unreachable_region(phase))) {
 528       // Yes,  the region will be removed during the next step below.
 529       // Cut the backedge input and remove phis since no data paths left.
 530       // We don't cut outputs to other nodes here since we need to put them
 531       // on the worklist.
 532       PhaseIterGVN *igvn = phase->is_IterGVN();
 533       if (in(1)->outcnt() == 1) {
 534         igvn->_worklist.push(in(1));
 535       }
 536       del_req(1);
 537       cnt = 0;
 538       assert( req() == 1, "no more inputs expected" );
 539       uint max = outcnt();
 540       bool progress = true;
 541       Node *top = phase->C->top();
 542       DUIterator j;
 543       while(progress) {
 544         progress = false;
 545         for (j = outs(); has_out(j); j++) {
 546           Node *n = out(j);
 547           if( n->is_Phi() ) {
 548             assert( igvn->eqv(n->in(0), this), "" );
 549             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 550             // Break dead loop data path.
 551             // Eagerly replace phis with top to avoid phis copies generation.
 552             igvn->replace_node(n, top);
 553             if( max != outcnt() ) {
 554               progress = true;
 555               j = refresh_out_pos(j);
 556               max = outcnt();
 557             }
 558           }
 559         }
 560       }
 561       add_to_worklist = true;
 562     }
 563   }
 564   if (add_to_worklist) {
 565     phase->is_IterGVN()->add_users_to_worklist(this); // Revisit collapsed Phis
 566   }
 567 
 568   if( cnt <= 1 ) {              // Only 1 path in?
 569     set_req(0, NULL);           // Null control input for region copy
 570     if( cnt == 0 && !can_reshape) { // Parse phase - leave the node as it is.
 571       // No inputs or all inputs are NULL.
 572       return NULL;
 573     } else if (can_reshape) {   // Optimization phase - remove the node
 574       PhaseIterGVN *igvn = phase->is_IterGVN();
 575       // Strip mined (inner) loop is going away, remove outer loop.
 576       if (is_CountedLoop() &&
 577           as_Loop()->is_strip_mined()) {
 578         Node* outer_sfpt = as_CountedLoop()->outer_safepoint();
 579         Node* outer_out = as_CountedLoop()->outer_loop_exit();
 580         if (outer_sfpt != NULL && outer_out != NULL) {
 581           Node* in = outer_sfpt->in(0);
 582           igvn->replace_node(outer_out, in);
 583           LoopNode* outer = as_CountedLoop()->outer_loop();
 584           igvn->replace_input_of(outer, LoopNode::LoopBackControl, igvn->C->top());
 585         }
 586       }
 587       Node *parent_ctrl;
 588       if( cnt == 0 ) {
 589         assert( req() == 1, "no inputs expected" );
 590         // During IGVN phase such region will be subsumed by TOP node
 591         // so region's phis will have TOP as control node.
 592         // Kill phis here to avoid it. PhiNode::is_copy() will be always false.
 593         // Also set other user's input to top.
 594         parent_ctrl = phase->C->top();
 595       } else {
 596         // The fallthrough case since we already checked dead loops above.
 597         parent_ctrl = in(1);
 598         assert(parent_ctrl != NULL, "Region is a copy of some non-null control");
 599         assert(!igvn->eqv(parent_ctrl, this), "Close dead loop");
 600       }
 601       if (!add_to_worklist)
 602         igvn->add_users_to_worklist(this); // Check for further allowed opts
 603       for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
 604         Node* n = last_out(i);
 605         igvn->hash_delete(n); // Remove from worklist before modifying edges
 606         if( n->is_Phi() ) {   // Collapse all Phis
 607           // Eagerly replace phis to avoid copies generation.
 608           Node* in;
 609           if( cnt == 0 ) {
 610             assert( n->req() == 1, "No data inputs expected" );
 611             in = parent_ctrl; // replaced by top
 612           } else {
 613             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 614             in = n->in(1);               // replaced by unique input
 615             if( n->as_Phi()->is_unsafe_data_reference(in) )
 616               in = phase->C->top();      // replaced by top
 617           }
 618           igvn->replace_node(n, in);
 619         }
 620         else if( n->is_Region() ) { // Update all incoming edges
 621           assert( !igvn->eqv(n, this), "Must be removed from DefUse edges");
 622           uint uses_found = 0;
 623           for( uint k=1; k < n->req(); k++ ) {
 624             if( n->in(k) == this ) {
 625               n->set_req(k, parent_ctrl);
 626               uses_found++;
 627             }
 628           }
 629           if( uses_found > 1 ) { // (--i) done at the end of the loop.
 630             i -= (uses_found - 1);
 631           }
 632         }
 633         else {
 634           assert( igvn->eqv(n->in(0), this), "Expect RegionNode to be control parent");
 635           n->set_req(0, parent_ctrl);
 636         }
 637 #ifdef ASSERT
 638         for( uint k=0; k < n->req(); k++ ) {
 639           assert( !igvn->eqv(n->in(k), this), "All uses of RegionNode should be gone");
 640         }
 641 #endif
 642       }
 643       // Remove the RegionNode itself from DefUse info
 644       igvn->remove_dead_node(this);
 645       return NULL;
 646     }
 647     return this;                // Record progress
 648   }
 649 
 650 
 651   // If a Region flows into a Region, merge into one big happy merge.
 652   if (can_reshape) {
 653     Node *m = merge_region(this, phase);
 654     if (m != NULL)  return m;
 655   }
 656 
 657   // Check if this region is the root of a clipping idiom on floats
 658   if( ConvertFloat2IntClipping && can_reshape && req() == 4 ) {
 659     // Check that only one use is a Phi and that it simplifies to two constants +
 660     PhiNode* phi = has_unique_phi();
 661     if (phi != NULL) {          // One Phi user
 662       // Check inputs to the Phi
 663       ConNode *min;
 664       ConNode *max;
 665       Node    *val;
 666       uint     min_idx;
 667       uint     max_idx;
 668       uint     val_idx;
 669       if( check_phi_clipping( phi, min, min_idx, max, max_idx, val, val_idx )  ) {
 670         IfNode *top_if;
 671         IfNode *bot_if;
 672         if( check_if_clipping( this, bot_if, top_if ) ) {
 673           // Control pattern checks, now verify compares
 674           Node   *top_in = NULL;   // value being compared against
 675           Node   *bot_in = NULL;
 676           if( check_compare_clipping( true,  bot_if, min, bot_in ) &&
 677               check_compare_clipping( false, top_if, max, top_in ) ) {
 678             if( bot_in == top_in ) {
 679               PhaseIterGVN *gvn = phase->is_IterGVN();
 680               assert( gvn != NULL, "Only had DefUse info in IterGVN");
 681               // Only remaining check is that bot_in == top_in == (Phi's val + mods)
 682 
 683               // Check for the ConvF2INode
 684               ConvF2INode *convf2i;
 685               if( check_convf2i_clipping( phi, val_idx, convf2i, min, max ) &&
 686                 convf2i->in(1) == bot_in ) {
 687                 // Matched pattern, including LShiftI; RShiftI, replace with integer compares
 688                 // max test
 689                 Node *cmp   = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, min ));
 690                 Node *boo   = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::lt ));
 691                 IfNode *iff = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( top_if->in(0), boo, PROB_UNLIKELY_MAG(5), top_if->_fcnt ));
 692                 Node *if_min= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 693                 Node *ifF   = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 694                 // min test
 695                 cmp         = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, max ));
 696                 boo         = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::gt ));
 697                 iff         = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( ifF, boo, PROB_UNLIKELY_MAG(5), bot_if->_fcnt ));
 698                 Node *if_max= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 699                 ifF         = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 700                 // update input edges to region node
 701                 set_req_X( min_idx, if_min, gvn );
 702                 set_req_X( max_idx, if_max, gvn );
 703                 set_req_X( val_idx, ifF,    gvn );
 704                 // remove unnecessary 'LShiftI; RShiftI' idiom
 705                 gvn->hash_delete(phi);
 706                 phi->set_req_X( val_idx, convf2i, gvn );
 707                 gvn->hash_find_insert(phi);
 708                 // Return transformed region node
 709                 return this;
 710               }
 711             }
 712           }
 713         }
 714       }
 715     }
 716   }
 717 
 718   if (can_reshape) {
 719     modified |= optimize_trichotomy(phase->is_IterGVN());
 720   }
 721 
 722   return modified ? this : NULL;
 723 }
 724 
 725 //------------------------------optimize_trichotomy--------------------------
 726 // Optimize nested comparisons of the following kind:
 727 //
 728 // int compare(int a, int b) {
 729 //   return (a < b) ? -1 : (a == b) ? 0 : 1;
 730 // }
 731 //
 732 // Shape 1:
 733 // if (compare(a, b) == 1) { ... } -> if (a > b) { ... }
 734 //
 735 // Shape 2:
 736 // if (compare(a, b) == 0) { ... } -> if (a == b) { ... }
 737 //
 738 // Above code leads to the following IR shapes where both Ifs compare the
 739 // same value and two out of three region inputs idx1 and idx2 map to
 740 // the same value and control flow.
 741 //
 742 // (1)   If                 (2)   If
 743 //      /  \                     /  \
 744 //   Proj  Proj               Proj  Proj
 745 //     |      \                |      \
 746 //     |       If              |      If                      If
 747 //     |      /  \             |     /  \                    /  \
 748 //     |   Proj  Proj          |  Proj  Proj      ==>     Proj  Proj
 749 //     |   /      /            \    |    /                  |    /
 750 //    Region     /              \   |   /                   |   /
 751 //         \    /                \  |  /                    |  /
 752 //         Region                Region                    Region
 753 //
 754 // The method returns true if 'this' is modified and false otherwise.
 755 bool RegionNode::optimize_trichotomy(PhaseIterGVN* igvn) {
 756   int idx1 = 1, idx2 = 2;
 757   Node* region = NULL;
 758   if (req() == 3 && in(1) != NULL && in(2) != NULL) {
 759     // Shape 1: Check if one of the inputs is a region that merges two control
 760     // inputs and has no other users (especially no Phi users).
 761     region = in(1)->isa_Region() ? in(1) : in(2)->isa_Region();
 762     if (region == NULL || region->outcnt() != 2 || region->req() != 3) {
 763       return false; // No suitable region input found
 764     }
 765   } else if (req() == 4) {
 766     // Shape 2: Check if two control inputs map to the same value of the unique phi
 767     // user and treat these as if they would come from another region (shape (1)).
 768     PhiNode* phi = has_unique_phi();
 769     if (phi == NULL) {
 770       return false; // No unique phi user
 771     }
 772     if (phi->in(idx1) != phi->in(idx2)) {
 773       idx2 = 3;
 774       if (phi->in(idx1) != phi->in(idx2)) {
 775         idx1 = 2;
 776         if (phi->in(idx1) != phi->in(idx2)) {
 777           return false; // No equal phi inputs found
 778         }
 779       }
 780     }
 781     assert(phi->in(idx1) == phi->in(idx2), "must be"); // Region is merging same value
 782     region = this;
 783   }
 784   if (region == NULL || region->in(idx1) == NULL || region->in(idx2) == NULL) {
 785     return false; // Region does not merge two control inputs
 786   }
 787   // At this point we know that region->in(idx1) and region->(idx2) map to the same
 788   // value and control flow. Now search for ifs that feed into these region inputs.
 789   ProjNode* proj1 = region->in(idx1)->isa_Proj();
 790   ProjNode* proj2 = region->in(idx2)->isa_Proj();
 791   if (proj1 == NULL || proj1->outcnt() != 1 ||
 792       proj2 == NULL || proj2->outcnt() != 1) {
 793     return false; // No projection inputs with region as unique user found
 794   }
 795   assert(proj1 != proj2, "should be different projections");
 796   IfNode* iff1 = proj1->in(0)->isa_If();
 797   IfNode* iff2 = proj2->in(0)->isa_If();
 798   if (iff1 == NULL || iff1->outcnt() != 2 ||
 799       iff2 == NULL || iff2->outcnt() != 2) {
 800     return false; // No ifs found
 801   }
 802   if (iff1 == iff2) {
 803     igvn->add_users_to_worklist(iff1); // Make sure dead if is eliminated
 804     igvn->replace_input_of(region, idx1, iff1->in(0));
 805     igvn->replace_input_of(region, idx2, igvn->C->top());
 806     return (region == this); // Remove useless if (both projections map to the same control/value)
 807   }
 808   BoolNode* bol1 = iff1->in(1)->isa_Bool();
 809   BoolNode* bol2 = iff2->in(1)->isa_Bool();
 810   if (bol1 == NULL || bol2 == NULL) {
 811     return false; // No bool inputs found
 812   }
 813   Node* cmp1 = bol1->in(1);
 814   Node* cmp2 = bol2->in(1);
 815   bool commute = false;
 816   if (!cmp1->is_Cmp() || !cmp2->is_Cmp()) {
 817     return false; // No comparison
 818   } else if (cmp1->Opcode() == Op_CmpF || cmp1->Opcode() == Op_CmpD ||
 819              cmp2->Opcode() == Op_CmpF || cmp2->Opcode() == Op_CmpD ||
 820              cmp1->Opcode() == Op_CmpP || cmp1->Opcode() == Op_CmpN ||
 821              cmp2->Opcode() == Op_CmpP || cmp2->Opcode() == Op_CmpN) {
 822     // Floats and pointers don't exactly obey trichotomy. To be on the safe side, don't transform their tests.
 823     return false;
 824   } else if (cmp1 != cmp2) {
 825     if (cmp1->in(1) == cmp2->in(2) &&
 826         cmp1->in(2) == cmp2->in(1)) {
 827       commute = true; // Same but swapped inputs, commute the test
 828     } else {
 829       return false; // Ifs are not comparing the same values
 830     }
 831   }
 832   proj1 = proj1->other_if_proj();
 833   proj2 = proj2->other_if_proj();
 834   if (!((proj1->unique_ctrl_out() == iff2 &&
 835          proj2->unique_ctrl_out() == this) ||
 836         (proj2->unique_ctrl_out() == iff1 &&
 837          proj1->unique_ctrl_out() == this))) {
 838     return false; // Ifs are not connected through other projs
 839   }
 840   // Found 'iff -> proj -> iff -> proj -> this' shape where all other projs are merged
 841   // through 'region' and map to the same value. Merge the boolean tests and replace
 842   // the ifs by a single comparison.
 843   BoolTest test1 = (proj1->_con == 1) ? bol1->_test : bol1->_test.negate();
 844   BoolTest test2 = (proj2->_con == 1) ? bol2->_test : bol2->_test.negate();
 845   test1 = commute ? test1.commute() : test1;
 846   // After possibly commuting test1, if we can merge test1 & test2, then proj2/iff2/bol2 are the nodes to refine.
 847   BoolTest::mask res = test1.merge(test2);
 848   if (res == BoolTest::illegal) {
 849     return false; // Unable to merge tests
 850   }
 851   // Adjust iff1 to always pass (only iff2 will remain)
 852   igvn->replace_input_of(iff1, 1, igvn->intcon(proj1->_con));
 853   if (res == BoolTest::never) {
 854     // Merged test is always false, adjust iff2 to always fail
 855     igvn->replace_input_of(iff2, 1, igvn->intcon(1 - proj2->_con));
 856   } else {
 857     // Replace bool input of iff2 with merged test
 858     BoolNode* new_bol = new BoolNode(bol2->in(1), res);
 859     igvn->replace_input_of(iff2, 1, igvn->transform((proj2->_con == 1) ? new_bol : new_bol->negate(igvn)));
 860   }
 861   return false;
 862 }
 863 
 864 const RegMask &RegionNode::out_RegMask() const {
 865   return RegMask::Empty;
 866 }
 867 
 868 // Find the one non-null required input.  RegionNode only
 869 Node *Node::nonnull_req() const {
 870   assert( is_Region(), "" );
 871   for( uint i = 1; i < _cnt; i++ )
 872     if( in(i) )
 873       return in(i);
 874   ShouldNotReachHere();
 875   return NULL;
 876 }
 877 
 878 
 879 //=============================================================================
 880 // note that these functions assume that the _adr_type field is flattened
 881 uint PhiNode::hash() const {
 882   const Type* at = _adr_type;
 883   return TypeNode::hash() + (at ? at->hash() : 0);
 884 }
 885 bool PhiNode::cmp( const Node &n ) const {
 886   return TypeNode::cmp(n) && _adr_type == ((PhiNode&)n)._adr_type;
 887 }
 888 static inline
 889 const TypePtr* flatten_phi_adr_type(const TypePtr* at) {
 890   if (at == NULL || at == TypePtr::BOTTOM)  return at;
 891   return Compile::current()->alias_type(at)->adr_type();
 892 }
 893 
 894 //----------------------------make---------------------------------------------
 895 // create a new phi with edges matching r and set (initially) to x
 896 PhiNode* PhiNode::make(Node* r, Node* x, const Type *t, const TypePtr* at) {
 897   uint preds = r->req();   // Number of predecessor paths
 898   assert(t != Type::MEMORY || at == flatten_phi_adr_type(at), "flatten at");
 899   PhiNode* p = new PhiNode(r, t, at);
 900   for (uint j = 1; j < preds; j++) {
 901     // Fill in all inputs, except those which the region does not yet have
 902     if (r->in(j) != NULL)
 903       p->init_req(j, x);
 904   }
 905   return p;
 906 }
 907 PhiNode* PhiNode::make(Node* r, Node* x) {
 908   const Type*    t  = x->bottom_type();
 909   const TypePtr* at = NULL;
 910   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 911   return make(r, x, t, at);
 912 }
 913 PhiNode* PhiNode::make_blank(Node* r, Node* x) {
 914   const Type*    t  = x->bottom_type();
 915   const TypePtr* at = NULL;
 916   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
 917   return new PhiNode(r, t, at);
 918 }
 919 
 920 
 921 //------------------------slice_memory-----------------------------------------
 922 // create a new phi with narrowed memory type
 923 PhiNode* PhiNode::slice_memory(const TypePtr* adr_type) const {
 924   PhiNode* mem = (PhiNode*) clone();
 925   *(const TypePtr**)&mem->_adr_type = adr_type;
 926   // convert self-loops, or else we get a bad graph
 927   for (uint i = 1; i < req(); i++) {
 928     if ((const Node*)in(i) == this)  mem->set_req(i, mem);
 929   }
 930   mem->verify_adr_type();
 931   return mem;
 932 }
 933 
 934 //------------------------split_out_instance-----------------------------------
 935 // Split out an instance type from a bottom phi.
 936 PhiNode* PhiNode::split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const {
 937   const TypeOopPtr *t_oop = at->isa_oopptr();
 938   assert(t_oop != NULL && t_oop->is_known_instance(), "expecting instance oopptr");
 939   const TypePtr *t = adr_type();
 940   assert(type() == Type::MEMORY &&
 941          (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 942           t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 943           t->is_oopptr()->cast_to_exactness(true)
 944            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 945            ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop),
 946          "bottom or raw memory required");
 947 
 948   // Check if an appropriate node already exists.
 949   Node *region = in(0);
 950   for (DUIterator_Fast kmax, k = region->fast_outs(kmax); k < kmax; k++) {
 951     Node* use = region->fast_out(k);
 952     if( use->is_Phi()) {
 953       PhiNode *phi2 = use->as_Phi();
 954       if (phi2->type() == Type::MEMORY && phi2->adr_type() == at) {
 955         return phi2;
 956       }
 957     }
 958   }
 959   Compile *C = igvn->C;
 960   Arena *a = Thread::current()->resource_area();
 961   Node_Array node_map = new Node_Array(a);
 962   Node_Stack stack(a, C->live_nodes() >> 4);
 963   PhiNode *nphi = slice_memory(at);
 964   igvn->register_new_node_with_optimizer( nphi );
 965   node_map.map(_idx, nphi);
 966   stack.push((Node *)this, 1);
 967   while(!stack.is_empty()) {
 968     PhiNode *ophi = stack.node()->as_Phi();
 969     uint i = stack.index();
 970     assert(i >= 1, "not control edge");
 971     stack.pop();
 972     nphi = node_map[ophi->_idx]->as_Phi();
 973     for (; i < ophi->req(); i++) {
 974       Node *in = ophi->in(i);
 975       if (in == NULL || igvn->type(in) == Type::TOP)
 976         continue;
 977       Node *opt = MemNode::optimize_simple_memory_chain(in, t_oop, NULL, igvn);
 978       PhiNode *optphi = opt->is_Phi() ? opt->as_Phi() : NULL;
 979       if (optphi != NULL && optphi->adr_type() == TypePtr::BOTTOM) {
 980         opt = node_map[optphi->_idx];
 981         if (opt == NULL) {
 982           stack.push(ophi, i);
 983           nphi = optphi->slice_memory(at);
 984           igvn->register_new_node_with_optimizer( nphi );
 985           node_map.map(optphi->_idx, nphi);
 986           ophi = optphi;
 987           i = 0; // will get incremented at top of loop
 988           continue;
 989         }
 990       }
 991       nphi->set_req(i, opt);
 992     }
 993   }
 994   return nphi;
 995 }
 996 
 997 //------------------------verify_adr_type--------------------------------------
 998 #ifdef ASSERT
 999 void PhiNode::verify_adr_type(VectorSet& visited, const TypePtr* at) const {
1000   if (visited.test_set(_idx))  return;  //already visited
1001 
1002   // recheck constructor invariants:
1003   verify_adr_type(false);
1004 
1005   // recheck local phi/phi consistency:
1006   assert(_adr_type == at || _adr_type == TypePtr::BOTTOM,
1007          "adr_type must be consistent across phi nest");
1008 
1009   // walk around
1010   for (uint i = 1; i < req(); i++) {
1011     Node* n = in(i);
1012     if (n == NULL)  continue;
1013     const Node* np = in(i);
1014     if (np->is_Phi()) {
1015       np->as_Phi()->verify_adr_type(visited, at);
1016     } else if (n->bottom_type() == Type::TOP
1017                || (n->is_Mem() && n->in(MemNode::Address)->bottom_type() == Type::TOP)) {
1018       // ignore top inputs
1019     } else {
1020       const TypePtr* nat = flatten_phi_adr_type(n->adr_type());
1021       // recheck phi/non-phi consistency at leaves:
1022       assert((nat != NULL) == (at != NULL), "");
1023       assert(nat == at || nat == TypePtr::BOTTOM,
1024              "adr_type must be consistent at leaves of phi nest");
1025     }
1026   }
1027 }
1028 
1029 // Verify a whole nest of phis rooted at this one.
1030 void PhiNode::verify_adr_type(bool recursive) const {
1031   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
1032   if (Node::in_dump())               return;  // muzzle asserts when printing
1033 
1034   assert((_type == Type::MEMORY) == (_adr_type != NULL), "adr_type for memory phis only");
1035 
1036   if (!VerifyAliases)       return;  // verify thoroughly only if requested
1037 
1038   assert(_adr_type == flatten_phi_adr_type(_adr_type),
1039          "Phi::adr_type must be pre-normalized");
1040 
1041   if (recursive) {
1042     VectorSet visited;
1043     verify_adr_type(visited, _adr_type);
1044   }
1045 }
1046 #endif
1047 
1048 
1049 //------------------------------Value------------------------------------------
1050 // Compute the type of the PhiNode
1051 const Type* PhiNode::Value(PhaseGVN* phase) const {
1052   Node *r = in(0);              // RegionNode
1053   if( !r )                      // Copy or dead
1054     return in(1) ? phase->type(in(1)) : Type::TOP;
1055 
1056   // Note: During parsing, phis are often transformed before their regions.
1057   // This means we have to use type_or_null to defend against untyped regions.
1058   if( phase->type_or_null(r) == Type::TOP )  // Dead code?
1059     return Type::TOP;
1060 
1061   // Check for trip-counted loop.  If so, be smarter.
1062   CountedLoopNode* l = r->is_CountedLoop() ? r->as_CountedLoop() : NULL;
1063   if (l && ((const Node*)l->phi() == this)) { // Trip counted loop!
1064     // protect against init_trip() or limit() returning NULL
1065     if (l->can_be_counted_loop(phase)) {
1066       const Node *init   = l->init_trip();
1067       const Node *limit  = l->limit();
1068       const Node* stride = l->stride();
1069       if (init != NULL && limit != NULL && stride != NULL) {
1070         const TypeInt* lo = phase->type(init)->isa_int();
1071         const TypeInt* hi = phase->type(limit)->isa_int();
1072         const TypeInt* stride_t = phase->type(stride)->isa_int();
1073         if (lo != NULL && hi != NULL && stride_t != NULL) { // Dying loops might have TOP here
1074           assert(stride_t->_hi >= stride_t->_lo, "bad stride type");
1075           BoolTest::mask bt = l->loopexit()->test_trip();
1076           // If the loop exit condition is "not equal", the condition
1077           // would not trigger if init > limit (if stride > 0) or if
1078           // init < limit if (stride > 0) so we can't deduce bounds
1079           // for the iv from the exit condition.
1080           if (bt != BoolTest::ne) {
1081             if (stride_t->_hi < 0) {          // Down-counter loop
1082               swap(lo, hi);
1083               return TypeInt::make(MIN2(lo->_lo, hi->_lo) , hi->_hi, 3)->filter_speculative(_type);
1084             } else if (stride_t->_lo >= 0) {
1085               return TypeInt::make(lo->_lo, MAX2(lo->_hi, hi->_hi), 3)->filter_speculative(_type);
1086             }
1087           }
1088         }
1089       }
1090     } else if (l->in(LoopNode::LoopBackControl) != NULL &&
1091                in(LoopNode::EntryControl) != NULL &&
1092                phase->type(l->in(LoopNode::LoopBackControl)) == Type::TOP) {
1093       // During CCP, if we saturate the type of a counted loop's Phi
1094       // before the special code for counted loop above has a chance
1095       // to run (that is as long as the type of the backedge's control
1096       // is top), we might end up with non monotonic types
1097       return phase->type(in(LoopNode::EntryControl))->filter_speculative(_type);
1098     }
1099   }
1100 
1101   // Until we have harmony between classes and interfaces in the type
1102   // lattice, we must tread carefully around phis which implicitly
1103   // convert the one to the other.
1104   const TypePtr* ttp = _type->make_ptr();
1105   const TypeInstPtr* ttip = (ttp != NULL) ? ttp->isa_instptr() : NULL;
1106   const TypeKlassPtr* ttkp = (ttp != NULL) ? ttp->isa_klassptr() : NULL;
1107   bool is_intf = false;
1108   if (ttip != NULL) {
1109     ciKlass* k = ttip->klass();
1110     if (k->is_loaded() && k->is_interface())
1111       is_intf = true;
1112   }
1113   if (ttkp != NULL) {
1114     ciKlass* k = ttkp->klass();
1115     if (k->is_loaded() && k->is_interface())
1116       is_intf = true;
1117   }
1118 
1119   // Default case: merge all inputs
1120   const Type *t = Type::TOP;        // Merged type starting value
1121   for (uint i = 1; i < req(); ++i) {// For all paths in
1122     // Reachable control path?
1123     if (r->in(i) && phase->type(r->in(i)) == Type::CONTROL) {
1124       const Type* ti = phase->type(in(i));
1125       // We assume that each input of an interface-valued Phi is a true
1126       // subtype of that interface.  This might not be true of the meet
1127       // of all the input types.  The lattice is not distributive in
1128       // such cases.  Ward off asserts in type.cpp by refusing to do
1129       // meets between interfaces and proper classes.
1130       const TypePtr* tip = ti->make_ptr();
1131       const TypeInstPtr* tiip = (tip != NULL) ? tip->isa_instptr() : NULL;
1132       if (tiip) {
1133         bool ti_is_intf = false;
1134         ciKlass* k = tiip->klass();
1135         if (k->is_loaded() && k->is_interface())
1136           ti_is_intf = true;
1137         if (is_intf != ti_is_intf)
1138           { t = _type; break; }
1139       }
1140       t = t->meet_speculative(ti);
1141     }
1142   }
1143 
1144   // The worst-case type (from ciTypeFlow) should be consistent with "t".
1145   // That is, we expect that "t->higher_equal(_type)" holds true.
1146   // There are various exceptions:
1147   // - Inputs which are phis might in fact be widened unnecessarily.
1148   //   For example, an input might be a widened int while the phi is a short.
1149   // - Inputs might be BotPtrs but this phi is dependent on a null check,
1150   //   and postCCP has removed the cast which encodes the result of the check.
1151   // - The type of this phi is an interface, and the inputs are classes.
1152   // - Value calls on inputs might produce fuzzy results.
1153   //   (Occurrences of this case suggest improvements to Value methods.)
1154   //
1155   // It is not possible to see Type::BOTTOM values as phi inputs,
1156   // because the ciTypeFlow pre-pass produces verifier-quality types.
1157   const Type* ft = t->filter_speculative(_type);  // Worst case type
1158 
1159 #ifdef ASSERT
1160   // The following logic has been moved into TypeOopPtr::filter.
1161   const Type* jt = t->join_speculative(_type);
1162   if (jt->empty()) {           // Emptied out???
1163 
1164     // Check for evil case of 't' being a class and '_type' expecting an
1165     // interface.  This can happen because the bytecodes do not contain
1166     // enough type info to distinguish a Java-level interface variable
1167     // from a Java-level object variable.  If we meet 2 classes which
1168     // both implement interface I, but their meet is at 'j/l/O' which
1169     // doesn't implement I, we have no way to tell if the result should
1170     // be 'I' or 'j/l/O'.  Thus we'll pick 'j/l/O'.  If this then flows
1171     // into a Phi which "knows" it's an Interface type we'll have to
1172     // uplift the type.
1173     if (!t->empty() && ttip && ttip->is_loaded() && ttip->klass()->is_interface()) {
1174       assert(ft == _type, ""); // Uplift to interface
1175     } else if (!t->empty() && ttkp && ttkp->is_loaded() && ttkp->klass()->is_interface()) {
1176       assert(ft == _type, ""); // Uplift to interface
1177     } else {
1178       // We also have to handle 'evil cases' of interface- vs. class-arrays
1179       Type::get_arrays_base_elements(jt, _type, NULL, &ttip);
1180       if (!t->empty() && ttip != NULL && ttip->is_loaded() && ttip->klass()->is_interface()) {
1181           assert(ft == _type, "");   // Uplift to array of interface
1182       } else {
1183         // Otherwise it's something stupid like non-overlapping int ranges
1184         // found on dying counted loops.
1185         assert(ft == Type::TOP, ""); // Canonical empty value
1186       }
1187     }
1188   }
1189 
1190   else {
1191 
1192     // If we have an interface-typed Phi and we narrow to a class type, the join
1193     // should report back the class.  However, if we have a J/L/Object
1194     // class-typed Phi and an interface flows in, it's possible that the meet &
1195     // join report an interface back out.  This isn't possible but happens
1196     // because the type system doesn't interact well with interfaces.
1197     const TypePtr *jtp = jt->make_ptr();
1198     const TypeInstPtr *jtip = (jtp != NULL) ? jtp->isa_instptr() : NULL;
1199     const TypeKlassPtr *jtkp = (jtp != NULL) ? jtp->isa_klassptr() : NULL;
1200     if( jtip && ttip ) {
1201       if( jtip->is_loaded() &&  jtip->klass()->is_interface() &&
1202           ttip->is_loaded() && !ttip->klass()->is_interface() ) {
1203         assert(ft == ttip->cast_to_ptr_type(jtip->ptr()) ||
1204                ft->isa_narrowoop() && ft->make_ptr() == ttip->cast_to_ptr_type(jtip->ptr()), "");
1205         jt = ft;
1206       }
1207     }
1208     if( jtkp && ttkp ) {
1209       if( jtkp->is_loaded() &&  jtkp->klass()->is_interface() &&
1210           !jtkp->klass_is_exact() && // Keep exact interface klass (6894807)
1211           ttkp->is_loaded() && !ttkp->klass()->is_interface() ) {
1212         assert(ft == ttkp->cast_to_ptr_type(jtkp->ptr()) ||
1213                ft->isa_narrowklass() && ft->make_ptr() == ttkp->cast_to_ptr_type(jtkp->ptr()), "");
1214         jt = ft;
1215       }
1216     }
1217     if (jt != ft && jt->base() == ft->base()) {
1218       if (jt->isa_int() &&
1219           jt->is_int()->_lo == ft->is_int()->_lo &&
1220           jt->is_int()->_hi == ft->is_int()->_hi)
1221         jt = ft;
1222       if (jt->isa_long() &&
1223           jt->is_long()->_lo == ft->is_long()->_lo &&
1224           jt->is_long()->_hi == ft->is_long()->_hi)
1225         jt = ft;
1226     }
1227     if (jt != ft) {
1228       tty->print("merge type:  "); t->dump(); tty->cr();
1229       tty->print("kill type:   "); _type->dump(); tty->cr();
1230       tty->print("join type:   "); jt->dump(); tty->cr();
1231       tty->print("filter type: "); ft->dump(); tty->cr();
1232     }
1233     assert(jt == ft, "");
1234   }
1235 #endif //ASSERT
1236 
1237   // Deal with conversion problems found in data loops.
1238   ft = phase->saturate(ft, phase->type_or_null(this), _type);
1239 
1240   return ft;
1241 }
1242 
1243 
1244 //------------------------------is_diamond_phi---------------------------------
1245 // Does this Phi represent a simple well-shaped diamond merge?  Return the
1246 // index of the true path or 0 otherwise.
1247 // If check_control_only is true, do not inspect the If node at the
1248 // top, and return -1 (not an edge number) on success.
1249 int PhiNode::is_diamond_phi(bool check_control_only) const {
1250   // Check for a 2-path merge
1251   Node *region = in(0);
1252   if( !region ) return 0;
1253   if( region->req() != 3 ) return 0;
1254   if(         req() != 3 ) return 0;
1255   // Check that both paths come from the same If
1256   Node *ifp1 = region->in(1);
1257   Node *ifp2 = region->in(2);
1258   if( !ifp1 || !ifp2 ) return 0;
1259   Node *iff = ifp1->in(0);
1260   if( !iff || !iff->is_If() ) return 0;
1261   if( iff != ifp2->in(0) ) return 0;
1262   if (check_control_only)  return -1;
1263   // Check for a proper bool/cmp
1264   const Node *b = iff->in(1);
1265   if( !b->is_Bool() ) return 0;
1266   const Node *cmp = b->in(1);
1267   if( !cmp->is_Cmp() ) return 0;
1268 
1269   // Check for branching opposite expected
1270   if( ifp2->Opcode() == Op_IfTrue ) {
1271     assert( ifp1->Opcode() == Op_IfFalse, "" );
1272     return 2;
1273   } else {
1274     assert( ifp1->Opcode() == Op_IfTrue, "" );
1275     return 1;
1276   }
1277 }
1278 
1279 //----------------------------check_cmove_id-----------------------------------
1280 // Check for CMove'ing a constant after comparing against the constant.
1281 // Happens all the time now, since if we compare equality vs a constant in
1282 // the parser, we "know" the variable is constant on one path and we force
1283 // it.  Thus code like "if( x==0 ) {/*EMPTY*/}" ends up inserting a
1284 // conditional move: "x = (x==0)?0:x;".  Yucko.  This fix is slightly more
1285 // general in that we don't need constants.  Since CMove's are only inserted
1286 // in very special circumstances, we do it here on generic Phi's.
1287 Node* PhiNode::is_cmove_id(PhaseTransform* phase, int true_path) {
1288   assert(true_path !=0, "only diamond shape graph expected");
1289 
1290   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1291   // phi->region->if_proj->ifnode->bool->cmp
1292   Node*     region = in(0);
1293   Node*     iff    = region->in(1)->in(0);
1294   BoolNode* b      = iff->in(1)->as_Bool();
1295   Node*     cmp    = b->in(1);
1296   Node*     tval   = in(true_path);
1297   Node*     fval   = in(3-true_path);
1298   Node*     id     = CMoveNode::is_cmove_id(phase, cmp, tval, fval, b);
1299   if (id == NULL)
1300     return NULL;
1301 
1302   // Either value might be a cast that depends on a branch of 'iff'.
1303   // Since the 'id' value will float free of the diamond, either
1304   // decast or return failure.
1305   Node* ctl = id->in(0);
1306   if (ctl != NULL && ctl->in(0) == iff) {
1307     if (id->is_ConstraintCast()) {
1308       return id->in(1);
1309     } else {
1310       // Don't know how to disentangle this value.
1311       return NULL;
1312     }
1313   }
1314 
1315   return id;
1316 }
1317 
1318 //------------------------------Identity---------------------------------------
1319 // Check for Region being Identity.
1320 Node* PhiNode::Identity(PhaseGVN* phase) {
1321   // Check for no merging going on
1322   // (There used to be special-case code here when this->region->is_Loop.
1323   // It would check for a tributary phi on the backedge that the main phi
1324   // trivially, perhaps with a single cast.  The unique_input method
1325   // does all this and more, by reducing such tributaries to 'this'.)
1326   Node* uin = unique_input(phase, false);
1327   if (uin != NULL) {
1328     return uin;
1329   }
1330 
1331   int true_path = is_diamond_phi();
1332   if (true_path != 0) {
1333     Node* id = is_cmove_id(phase, true_path);
1334     if (id != NULL)  return id;
1335   }
1336 
1337   // Looking for phis with identical inputs.  If we find one that has
1338   // type TypePtr::BOTTOM, replace the current phi with the bottom phi.
1339   if (phase->is_IterGVN() && type() == Type::MEMORY && adr_type() !=
1340       TypePtr::BOTTOM && !adr_type()->is_known_instance()) {
1341     uint phi_len = req();
1342     Node* phi_reg = region();
1343     for (DUIterator_Fast imax, i = phi_reg->fast_outs(imax); i < imax; i++) {
1344       Node* u = phi_reg->fast_out(i);
1345       if (u->is_Phi() && u->as_Phi()->type() == Type::MEMORY &&
1346           u->adr_type() == TypePtr::BOTTOM && u->in(0) == phi_reg &&
1347           u->req() == phi_len) {
1348         for (uint j = 1; j < phi_len; j++) {
1349           if (in(j) != u->in(j)) {
1350             u = NULL;
1351             break;
1352           }
1353         }
1354         if (u != NULL) {
1355           return u;
1356         }
1357       }
1358     }
1359   }
1360 
1361   return this;                     // No identity
1362 }
1363 
1364 //-----------------------------unique_input------------------------------------
1365 // Find the unique value, discounting top, self-loops, and casts.
1366 // Return top if there are no inputs, and self if there are multiple.
1367 Node* PhiNode::unique_input(PhaseTransform* phase, bool uncast) {
1368   //  1) One unique direct input,
1369   // or if uncast is true:
1370   //  2) some of the inputs have an intervening ConstraintCast
1371   //  3) an input is a self loop
1372   //
1373   //  1) input   or   2) input     or   3) input __
1374   //     /   \           /   \               \  /  \
1375   //     \   /          |    cast             phi  cast
1376   //      phi            \   /               /  \  /
1377   //                      phi               /    --
1378 
1379   Node* r = in(0);                      // RegionNode
1380   if (r == NULL)  return in(1);         // Already degraded to a Copy
1381   Node* input = NULL; // The unique direct input (maybe uncasted = ConstraintCasts removed)
1382 
1383   for (uint i = 1, cnt = req(); i < cnt; ++i) {
1384     Node* rc = r->in(i);
1385     if (rc == NULL || phase->type(rc) == Type::TOP)
1386       continue;                 // ignore unreachable control path
1387     Node* n = in(i);
1388     if (n == NULL)
1389       continue;
1390     Node* un = n;
1391     if (uncast) {
1392 #ifdef ASSERT
1393       Node* m = un->uncast();
1394 #endif
1395       while (un != NULL && un->req() == 2 && un->is_ConstraintCast()) {
1396         Node* next = un->in(1);
1397         if (phase->type(next)->isa_rawptr() && phase->type(un)->isa_oopptr()) {
1398           // risk exposing raw ptr at safepoint
1399           break;
1400         }
1401         un = next;
1402       }
1403       assert(m == un || un->in(1) == m, "Only expected at CheckCastPP from allocation");
1404     }
1405     if (un == NULL || un == this || phase->type(un) == Type::TOP) {
1406       continue; // ignore if top, or in(i) and "this" are in a data cycle
1407     }
1408     // Check for a unique input (maybe uncasted)
1409     if (input == NULL) {
1410       input = un;
1411     } else if (input != un) {
1412       input = NodeSentinel; // no unique input
1413     }
1414   }
1415   if (input == NULL) {
1416     return phase->C->top();        // no inputs
1417   }
1418 
1419   if (input != NodeSentinel) {
1420     return input;           // one unique direct input
1421   }
1422 
1423   // Nothing.
1424   return NULL;
1425 }
1426 
1427 //------------------------------is_x2logic-------------------------------------
1428 // Check for simple convert-to-boolean pattern
1429 // If:(C Bool) Region:(IfF IfT) Phi:(Region 0 1)
1430 // Convert Phi to an ConvIB.
1431 static Node *is_x2logic( PhaseGVN *phase, PhiNode *phi, int true_path ) {
1432   assert(true_path !=0, "only diamond shape graph expected");
1433   // Convert the true/false index into an expected 0/1 return.
1434   // Map 2->0 and 1->1.
1435   int flipped = 2-true_path;
1436 
1437   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1438   // phi->region->if_proj->ifnode->bool->cmp
1439   Node *region = phi->in(0);
1440   Node *iff = region->in(1)->in(0);
1441   BoolNode *b = (BoolNode*)iff->in(1);
1442   const CmpNode *cmp = (CmpNode*)b->in(1);
1443 
1444   Node *zero = phi->in(1);
1445   Node *one  = phi->in(2);
1446   const Type *tzero = phase->type( zero );
1447   const Type *tone  = phase->type( one  );
1448 
1449   // Check for compare vs 0
1450   const Type *tcmp = phase->type(cmp->in(2));
1451   if( tcmp != TypeInt::ZERO && tcmp != TypePtr::NULL_PTR ) {
1452     // Allow cmp-vs-1 if the other input is bounded by 0-1
1453     if( !(tcmp == TypeInt::ONE && phase->type(cmp->in(1)) == TypeInt::BOOL) )
1454       return NULL;
1455     flipped = 1-flipped;        // Test is vs 1 instead of 0!
1456   }
1457 
1458   // Check for setting zero/one opposite expected
1459   if( tzero == TypeInt::ZERO ) {
1460     if( tone == TypeInt::ONE ) {
1461     } else return NULL;
1462   } else if( tzero == TypeInt::ONE ) {
1463     if( tone == TypeInt::ZERO ) {
1464       flipped = 1-flipped;
1465     } else return NULL;
1466   } else return NULL;
1467 
1468   // Check for boolean test backwards
1469   if( b->_test._test == BoolTest::ne ) {
1470   } else if( b->_test._test == BoolTest::eq ) {
1471     flipped = 1-flipped;
1472   } else return NULL;
1473 
1474   // Build int->bool conversion
1475   Node *n = new Conv2BNode(cmp->in(1));
1476   if( flipped )
1477     n = new XorINode( phase->transform(n), phase->intcon(1) );
1478 
1479   return n;
1480 }
1481 
1482 //------------------------------is_cond_add------------------------------------
1483 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"
1484 // To be profitable the control flow has to disappear; there can be no other
1485 // values merging here.  We replace the test-and-branch with:
1486 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by
1487 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.
1488 // Then convert Y to 0-or-Y and finally add.
1489 // This is a key transform for SpecJava _201_compress.
1490 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {
1491   assert(true_path !=0, "only diamond shape graph expected");
1492 
1493   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1494   // phi->region->if_proj->ifnode->bool->cmp
1495   RegionNode *region = (RegionNode*)phi->in(0);
1496   Node *iff = region->in(1)->in(0);
1497   BoolNode* b = iff->in(1)->as_Bool();
1498   const CmpNode *cmp = (CmpNode*)b->in(1);
1499 
1500   // Make sure only merging this one phi here
1501   if (region->has_unique_phi() != phi)  return NULL;
1502 
1503   // Make sure each arm of the diamond has exactly one output, which we assume
1504   // is the region.  Otherwise, the control flow won't disappear.
1505   if (region->in(1)->outcnt() != 1) return NULL;
1506   if (region->in(2)->outcnt() != 1) return NULL;
1507 
1508   // Check for "(P < Q)" of type signed int
1509   if (b->_test._test != BoolTest::lt)  return NULL;
1510   if (cmp->Opcode() != Op_CmpI)        return NULL;
1511 
1512   Node *p = cmp->in(1);
1513   Node *q = cmp->in(2);
1514   Node *n1 = phi->in(  true_path);
1515   Node *n2 = phi->in(3-true_path);
1516 
1517   int op = n1->Opcode();
1518   if( op != Op_AddI           // Need zero as additive identity
1519       /*&&op != Op_SubI &&
1520       op != Op_AddP &&
1521       op != Op_XorI &&
1522       op != Op_OrI*/ )
1523     return NULL;
1524 
1525   Node *x = n2;
1526   Node *y = NULL;
1527   if( x == n1->in(1) ) {
1528     y = n1->in(2);
1529   } else if( x == n1->in(2) ) {
1530     y = n1->in(1);
1531   } else return NULL;
1532 
1533   // Not so profitable if compare and add are constants
1534   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )
1535     return NULL;
1536 
1537   Node *cmplt = phase->transform( new CmpLTMaskNode(p,q) );
1538   Node *j_and   = phase->transform( new AndINode(cmplt,y) );
1539   return new AddINode(j_and,x);
1540 }
1541 
1542 //------------------------------is_absolute------------------------------------
1543 // Check for absolute value.
1544 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {
1545   assert(true_path !=0, "only diamond shape graph expected");
1546 
1547   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero
1548   int  phi_x_idx = 0;           // Index of phi input where to find naked x
1549 
1550   // ABS ends with the merge of 2 control flow paths.
1551   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.
1552   int false_path = 3 - true_path;
1553 
1554   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1555   // phi->region->if_proj->ifnode->bool->cmp
1556   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();
1557   Node *cmp = bol->in(1);
1558 
1559   // Check bool sense
1560   if (cmp->Opcode() == Op_CmpF || cmp->Opcode() == Op_CmpD) {
1561     switch (bol->_test._test) {
1562     case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;
1563     case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1564     case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1565     case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;
1566     default:           return NULL;                              break;
1567     }
1568   } else if (cmp->Opcode() == Op_CmpI || cmp->Opcode() == Op_CmpL) {
1569     switch (bol->_test._test) {
1570     case BoolTest::lt:
1571     case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1572     case BoolTest::gt:
1573     case BoolTest::ge: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1574     default:           return NULL;                              break;
1575     }
1576   }
1577 
1578   // Test is next
1579   const Type *tzero = NULL;
1580   switch (cmp->Opcode()) {
1581   case Op_CmpI:    tzero = TypeInt::ZERO; break;  // Integer ABS
1582   case Op_CmpL:    tzero = TypeLong::ZERO; break; // Long ABS
1583   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS
1584   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS
1585   default: return NULL;
1586   }
1587 
1588   // Find zero input of compare; the other input is being abs'd
1589   Node *x = NULL;
1590   bool flip = false;
1591   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {
1592     x = cmp->in(3 - cmp_zero_idx);
1593   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {
1594     // The test is inverted, we should invert the result...
1595     x = cmp->in(cmp_zero_idx);
1596     flip = true;
1597   } else {
1598     return NULL;
1599   }
1600 
1601   // Next get the 2 pieces being selected, one is the original value
1602   // and the other is the negated value.
1603   if( phi_root->in(phi_x_idx) != x ) return NULL;
1604 
1605   // Check other phi input for subtract node
1606   Node *sub = phi_root->in(3 - phi_x_idx);
1607 
1608   // Allow only Sub(0,X) and fail out for all others; Neg is not OK
1609   if( tzero == TypeF::ZERO ) {
1610     if( sub->Opcode() != Op_SubF ||
1611         sub->in(2) != x ||
1612         phase->type(sub->in(1)) != tzero ) return NULL;
1613     x = new AbsFNode(x);
1614     if (flip) {
1615       x = new SubFNode(sub->in(1), phase->transform(x));
1616     }
1617   } else if (tzero == TypeD::ZERO) {
1618     if( sub->Opcode() != Op_SubD ||
1619         sub->in(2) != x ||
1620         phase->type(sub->in(1)) != tzero ) return NULL;
1621     x = new AbsDNode(x);
1622     if (flip) {
1623       x = new SubDNode(sub->in(1), phase->transform(x));
1624     }
1625   } else if (tzero == TypeInt::ZERO) {
1626     if (sub->Opcode() != Op_SubI ||
1627         sub->in(2) != x ||
1628         phase->type(sub->in(1)) != tzero) return NULL;
1629     x = new AbsINode(x);
1630     if (flip) {
1631       x = new SubINode(sub->in(1), phase->transform(x));
1632     }
1633   } else {
1634     if (sub->Opcode() != Op_SubL ||
1635         sub->in(2) != x ||
1636         phase->type(sub->in(1)) != tzero) return NULL;
1637     x = new AbsLNode(x);
1638     if (flip) {
1639       x = new SubLNode(sub->in(1), phase->transform(x));
1640     }
1641   }
1642 
1643   return x;
1644 }
1645 
1646 //------------------------------split_once-------------------------------------
1647 // Helper for split_flow_path
1648 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {
1649   igvn->hash_delete(n);         // Remove from hash before hacking edges
1650 
1651   uint j = 1;
1652   for (uint i = phi->req()-1; i > 0; i--) {
1653     if (phi->in(i) == val) {   // Found a path with val?
1654       // Add to NEW Region/Phi, no DU info
1655       newn->set_req( j++, n->in(i) );
1656       // Remove from OLD Region/Phi
1657       n->del_req(i);
1658     }
1659   }
1660 
1661   // Register the new node but do not transform it.  Cannot transform until the
1662   // entire Region/Phi conglomerate has been hacked as a single huge transform.
1663   igvn->register_new_node_with_optimizer( newn );
1664 
1665   // Now I can point to the new node.
1666   n->add_req(newn);
1667   igvn->_worklist.push(n);
1668 }
1669 
1670 //------------------------------split_flow_path--------------------------------
1671 // Check for merging identical values and split flow paths
1672 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {
1673   BasicType bt = phi->type()->basic_type();
1674   if( bt == T_ILLEGAL || type2size[bt] <= 0 )
1675     return NULL;                // Bail out on funny non-value stuff
1676   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a
1677     return NULL;                // third unequal input to be worth doing
1678 
1679   // Scan for a constant
1680   uint i;
1681   for( i = 1; i < phi->req()-1; i++ ) {
1682     Node *n = phi->in(i);
1683     if( !n ) return NULL;
1684     if( phase->type(n) == Type::TOP ) return NULL;
1685     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN || n->Opcode() == Op_ConNKlass )
1686       break;
1687   }
1688   if( i >= phi->req() )         // Only split for constants
1689     return NULL;
1690 
1691   Node *val = phi->in(i);       // Constant to split for
1692   uint hit = 0;                 // Number of times it occurs
1693   Node *r = phi->region();
1694 
1695   for( ; i < phi->req(); i++ ){ // Count occurrences of constant
1696     Node *n = phi->in(i);
1697     if( !n ) return NULL;
1698     if( phase->type(n) == Type::TOP ) return NULL;
1699     if( phi->in(i) == val ) {
1700       hit++;
1701       if (PhaseIdealLoop::find_predicate(r->in(i)) != NULL) {
1702         return NULL;            // don't split loop entry path
1703       }
1704     }
1705   }
1706 
1707   if( hit <= 1 ||               // Make sure we find 2 or more
1708       hit == phi->req()-1 )     // and not ALL the same value
1709     return NULL;
1710 
1711   // Now start splitting out the flow paths that merge the same value.
1712   // Split first the RegionNode.
1713   PhaseIterGVN *igvn = phase->is_IterGVN();
1714   RegionNode *newr = new RegionNode(hit+1);
1715   split_once(igvn, phi, val, r, newr);
1716 
1717   // Now split all other Phis than this one
1718   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {
1719     Node* phi2 = r->fast_out(k);
1720     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {
1721       PhiNode *newphi = PhiNode::make_blank(newr, phi2);
1722       split_once(igvn, phi, val, phi2, newphi);
1723     }
1724   }
1725 
1726   // Clean up this guy
1727   igvn->hash_delete(phi);
1728   for( i = phi->req()-1; i > 0; i-- ) {
1729     if( phi->in(i) == val ) {
1730       phi->del_req(i);
1731     }
1732   }
1733   phi->add_req(val);
1734 
1735   return phi;
1736 }
1737 
1738 //=============================================================================
1739 //------------------------------simple_data_loop_check-------------------------
1740 //  Try to determining if the phi node in a simple safe/unsafe data loop.
1741 //  Returns:
1742 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
1743 // Safe       - safe case when the phi and it's inputs reference only safe data
1744 //              nodes;
1745 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there
1746 //              is no reference back to the phi - need a graph walk
1747 //              to determine if it is in a loop;
1748 // UnsafeLoop - unsafe case when the phi references itself directly or through
1749 //              unsafe data node.
1750 //  Note: a safe data node is a node which could/never reference itself during
1751 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.
1752 //  I mark Phi nodes as safe node not only because they can reference itself
1753 //  but also to prevent mistaking the fallthrough case inside an outer loop
1754 //  as dead loop when the phi references itselfs through an other phi.
1755 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {
1756   // It is unsafe loop if the phi node references itself directly.
1757   if (in == (Node*)this)
1758     return UnsafeLoop; // Unsafe loop
1759   // Unsafe loop if the phi node references itself through an unsafe data node.
1760   // Exclude cases with null inputs or data nodes which could reference
1761   // itself (safe for dead loops).
1762   if (in != NULL && !in->is_dead_loop_safe()) {
1763     // Check inputs of phi's inputs also.
1764     // It is much less expensive then full graph walk.
1765     uint cnt = in->req();
1766     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;
1767     for (; i < cnt; ++i) {
1768       Node* m = in->in(i);
1769       if (m == (Node*)this)
1770         return UnsafeLoop; // Unsafe loop
1771       if (m != NULL && !m->is_dead_loop_safe()) {
1772         // Check the most common case (about 30% of all cases):
1773         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).
1774         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : NULL;
1775         if (m1 == (Node*)this)
1776           return UnsafeLoop; // Unsafe loop
1777         if (m1 != NULL && m1 == m->in(2) &&
1778             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {
1779           continue; // Safe case
1780         }
1781         // The phi references an unsafe node - need full analysis.
1782         return Unsafe;
1783       }
1784     }
1785   }
1786   return Safe; // Safe case - we can optimize the phi node.
1787 }
1788 
1789 //------------------------------is_unsafe_data_reference-----------------------
1790 // If phi can be reached through the data input - it is data loop.
1791 bool PhiNode::is_unsafe_data_reference(Node *in) const {
1792   assert(req() > 1, "");
1793   // First, check simple cases when phi references itself directly or
1794   // through an other node.
1795   LoopSafety safety = simple_data_loop_check(in);
1796   if (safety == UnsafeLoop)
1797     return true;  // phi references itself - unsafe loop
1798   else if (safety == Safe)
1799     return false; // Safe case - phi could be replaced with the unique input.
1800 
1801   // Unsafe case when we should go through data graph to determine
1802   // if the phi references itself.
1803 
1804   ResourceMark rm;
1805 
1806   Node_List nstack;
1807   VectorSet visited;
1808 
1809   nstack.push(in); // Start with unique input.
1810   visited.set(in->_idx);
1811   while (nstack.size() != 0) {
1812     Node* n = nstack.pop();
1813     uint cnt = n->req();
1814     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;
1815     for (; i < cnt; i++) {
1816       Node* m = n->in(i);
1817       if (m == (Node*)this) {
1818         return true;    // Data loop
1819       }
1820       if (m != NULL && !m->is_dead_loop_safe()) { // Only look for unsafe cases.
1821         if (!visited.test_set(m->_idx))
1822           nstack.push(m);
1823       }
1824     }
1825   }
1826   return false; // The phi is not reachable from its inputs
1827 }
1828 
1829 // Is this Phi's region or some inputs to the region enqueued for IGVN
1830 // and so could cause the region to be optimized out?
1831 bool PhiNode::wait_for_region_igvn(PhaseGVN* phase) {
1832   PhaseIterGVN* igvn = phase->is_IterGVN();
1833   Unique_Node_List& worklist = igvn->_worklist;
1834   bool delay = false;
1835   Node* r = in(0);
1836   for (uint j = 1; j < req(); j++) {
1837     Node* rc = r->in(j);
1838     Node* n = in(j);
1839     if (rc != NULL &&
1840         rc->is_Proj()) {
1841       if (worklist.member(rc)) {
1842         delay = true;
1843       } else if (rc->in(0) != NULL &&
1844                  rc->in(0)->is_If()) {
1845         if (worklist.member(rc->in(0))) {
1846           delay = true;
1847         } else if (rc->in(0)->in(1) != NULL &&
1848                    rc->in(0)->in(1)->is_Bool()) {
1849           if (worklist.member(rc->in(0)->in(1))) {
1850             delay = true;
1851           } else if (rc->in(0)->in(1)->in(1) != NULL &&
1852                      rc->in(0)->in(1)->in(1)->is_Cmp()) {
1853             if (worklist.member(rc->in(0)->in(1)->in(1))) {
1854               delay = true;
1855             }
1856           }
1857         }
1858       }
1859     }
1860   }
1861   if (delay) {
1862     worklist.push(this);
1863   }
1864   return delay;
1865 }
1866 
1867 //------------------------------Ideal------------------------------------------
1868 // Return a node which is more "ideal" than the current node.  Must preserve
1869 // the CFG, but we can still strip out dead paths.
1870 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1871   // The next should never happen after 6297035 fix.
1872   if( is_copy() )               // Already degraded to a Copy ?
1873     return NULL;                // No change
1874 
1875   Node *r = in(0);              // RegionNode
1876   assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");
1877 
1878   // Note: During parsing, phis are often transformed before their regions.
1879   // This means we have to use type_or_null to defend against untyped regions.
1880   if( phase->type_or_null(r) == Type::TOP ) // Dead code?
1881     return NULL;                // No change
1882 
1883   Node *top = phase->C->top();
1884   bool new_phi = (outcnt() == 0); // transforming new Phi
1885   // No change for igvn if new phi is not hooked
1886   if (new_phi && can_reshape)
1887     return NULL;
1888 
1889   // The are 2 situations when only one valid phi's input is left
1890   // (in addition to Region input).
1891   // One: region is not loop - replace phi with this input.
1892   // Two: region is loop - replace phi with top since this data path is dead
1893   //                       and we need to break the dead data loop.
1894   Node* progress = NULL;        // Record if any progress made
1895   for( uint j = 1; j < req(); ++j ){ // For all paths in
1896     // Check unreachable control paths
1897     Node* rc = r->in(j);
1898     Node* n = in(j);            // Get the input
1899     if (rc == NULL || phase->type(rc) == Type::TOP) {
1900       if (n != top) {           // Not already top?
1901         PhaseIterGVN *igvn = phase->is_IterGVN();
1902         if (can_reshape && igvn != NULL) {
1903           igvn->_worklist.push(r);
1904         }
1905         // Nuke it down
1906         if (can_reshape) {
1907           set_req_X(j, top, igvn);
1908         } else {
1909           set_req(j, top);
1910         }
1911         progress = this;        // Record progress
1912       }
1913     }
1914   }
1915 
1916   if (can_reshape && outcnt() == 0) {
1917     // set_req() above may kill outputs if Phi is referenced
1918     // only by itself on the dead (top) control path.
1919     return top;
1920   }
1921 
1922   bool uncasted = false;
1923   Node* uin = unique_input(phase, false);
1924   if (uin == NULL && can_reshape &&
1925       // If there is a chance that the region can be optimized out do
1926       // not add a cast node that we can't remove yet.
1927       !wait_for_region_igvn(phase)) {
1928     uncasted = true;
1929     uin = unique_input(phase, true);
1930   }
1931   if (uin == top) {             // Simplest case: no alive inputs.
1932     if (can_reshape)            // IGVN transformation
1933       return top;
1934     else
1935       return NULL;              // Identity will return TOP
1936   } else if (uin != NULL) {
1937     // Only one not-NULL unique input path is left.
1938     // Determine if this input is backedge of a loop.
1939     // (Skip new phis which have no uses and dead regions).
1940     if (outcnt() > 0 && r->in(0) != NULL) {
1941       // First, take the short cut when we know it is a loop and
1942       // the EntryControl data path is dead.
1943       // Loop node may have only one input because entry path
1944       // is removed in PhaseIdealLoop::Dominators().
1945       assert(!r->is_Loop() || r->req() <= 3, "Loop node should have 3 or less inputs");
1946       bool is_loop = (r->is_Loop() && r->req() == 3);
1947       // Then, check if there is a data loop when phi references itself directly
1948       // or through other data nodes.
1949       if ((is_loop && !uin->eqv_uncast(in(LoopNode::EntryControl))) ||
1950           (!is_loop && is_unsafe_data_reference(uin))) {
1951         // Break this data loop to avoid creation of a dead loop.
1952         if (can_reshape) {
1953           return top;
1954         } else {
1955           // We can't return top if we are in Parse phase - cut inputs only
1956           // let Identity to handle the case.
1957           replace_edge(uin, top);
1958           return NULL;
1959         }
1960       }
1961     }
1962 
1963     if (uncasted) {
1964       // Add cast nodes between the phi to be removed and its unique input.
1965       // Wait until after parsing for the type information to propagate from the casts.
1966       assert(can_reshape, "Invalid during parsing");
1967       const Type* phi_type = bottom_type();
1968       assert(phi_type->isa_int() || phi_type->isa_ptr(), "bad phi type");
1969       // Add casts to carry the control dependency of the Phi that is
1970       // going away
1971       Node* cast = NULL;
1972       if (phi_type->isa_int()) {
1973         cast = ConstraintCastNode::make_cast(Op_CastII, r, uin, phi_type, true);
1974       } else {
1975         const Type* uin_type = phase->type(uin);
1976         if (!phi_type->isa_oopptr() && !uin_type->isa_oopptr()) {
1977           cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, true);
1978         } else {
1979           // Use a CastPP for a cast to not null and a CheckCastPP for
1980           // a cast to a new klass (and both if both null-ness and
1981           // klass change).
1982 
1983           // If the type of phi is not null but the type of uin may be
1984           // null, uin's type must be casted to not null
1985           if (phi_type->join(TypePtr::NOTNULL) == phi_type->remove_speculative() &&
1986               uin_type->join(TypePtr::NOTNULL) != uin_type->remove_speculative()) {
1987             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, TypePtr::NOTNULL, true);
1988           }
1989 
1990           // If the type of phi and uin, both casted to not null,
1991           // differ the klass of uin must be (check)cast'ed to match
1992           // that of phi
1993           if (phi_type->join_speculative(TypePtr::NOTNULL) != uin_type->join_speculative(TypePtr::NOTNULL)) {
1994             Node* n = uin;
1995             if (cast != NULL) {
1996               cast = phase->transform(cast);
1997               n = cast;
1998             }
1999             cast = ConstraintCastNode::make_cast(Op_CheckCastPP, r, n, phi_type, true);
2000           }
2001           if (cast == NULL) {
2002             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, true);
2003           }
2004         }
2005       }
2006       assert(cast != NULL, "cast should be set");
2007       cast = phase->transform(cast);
2008       // set all inputs to the new cast(s) so the Phi is removed by Identity
2009       PhaseIterGVN* igvn = phase->is_IterGVN();
2010       for (uint i = 1; i < req(); i++) {
2011         set_req_X(i, cast, igvn);
2012       }
2013       uin = cast;
2014     }
2015 
2016     // One unique input.
2017     debug_only(Node* ident = Identity(phase));
2018     // The unique input must eventually be detected by the Identity call.
2019 #ifdef ASSERT
2020     if (ident != uin && !ident->is_top()) {
2021       // print this output before failing assert
2022       r->dump(3);
2023       this->dump(3);
2024       ident->dump();
2025       uin->dump();
2026     }
2027 #endif
2028     assert(ident == uin || ident->is_top(), "Identity must clean this up");
2029     return NULL;
2030   }
2031 
2032   Node* opt = NULL;
2033   int true_path = is_diamond_phi();
2034   if( true_path != 0 ) {
2035     // Check for CMove'ing identity. If it would be unsafe,
2036     // handle it here. In the safe case, let Identity handle it.
2037     Node* unsafe_id = is_cmove_id(phase, true_path);
2038     if( unsafe_id != NULL && is_unsafe_data_reference(unsafe_id) )
2039       opt = unsafe_id;
2040 
2041     // Check for simple convert-to-boolean pattern
2042     if( opt == NULL )
2043       opt = is_x2logic(phase, this, true_path);
2044 
2045     // Check for absolute value
2046     if( opt == NULL )
2047       opt = is_absolute(phase, this, true_path);
2048 
2049     // Check for conditional add
2050     if( opt == NULL && can_reshape )
2051       opt = is_cond_add(phase, this, true_path);
2052 
2053     // These 4 optimizations could subsume the phi:
2054     // have to check for a dead data loop creation.
2055     if( opt != NULL ) {
2056       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {
2057         // Found dead loop.
2058         if( can_reshape )
2059           return top;
2060         // We can't return top if we are in Parse phase - cut inputs only
2061         // to stop further optimizations for this phi. Identity will return TOP.
2062         assert(req() == 3, "only diamond merge phi here");
2063         set_req(1, top);
2064         set_req(2, top);
2065         return NULL;
2066       } else {
2067         return opt;
2068       }
2069     }
2070   }
2071 
2072   // Check for merging identical values and split flow paths
2073   if (can_reshape) {
2074     opt = split_flow_path(phase, this);
2075     // This optimization only modifies phi - don't need to check for dead loop.
2076     assert(opt == NULL || phase->eqv(opt, this), "do not elide phi");
2077     if (opt != NULL)  return opt;
2078   }
2079 
2080   if (in(1) != NULL && in(1)->Opcode() == Op_AddP && can_reshape) {
2081     // Try to undo Phi of AddP:
2082     // (Phi (AddP base address offset) (AddP base2 address2 offset2))
2083     // becomes:
2084     // newbase := (Phi base base2)
2085     // newaddress := (Phi address address2)
2086     // newoffset := (Phi offset offset2)
2087     // (AddP newbase newaddress newoffset)
2088     //
2089     // This occurs as a result of unsuccessful split_thru_phi and
2090     // interferes with taking advantage of addressing modes. See the
2091     // clone_shift_expressions code in matcher.cpp
2092     Node* addp = in(1);
2093     Node* base = addp->in(AddPNode::Base);
2094     Node* address = addp->in(AddPNode::Address);
2095     Node* offset = addp->in(AddPNode::Offset);
2096     if (base != NULL && address != NULL && offset != NULL &&
2097         !base->is_top() && !address->is_top() && !offset->is_top()) {
2098       const Type* base_type = base->bottom_type();
2099       const Type* address_type = address->bottom_type();
2100       // make sure that all the inputs are similar to the first one,
2101       // i.e. AddP with base == address and same offset as first AddP
2102       bool doit = true;
2103       for (uint i = 2; i < req(); i++) {
2104         if (in(i) == NULL ||
2105             in(i)->Opcode() != Op_AddP ||
2106             in(i)->in(AddPNode::Base) == NULL ||
2107             in(i)->in(AddPNode::Address) == NULL ||
2108             in(i)->in(AddPNode::Offset) == NULL ||
2109             in(i)->in(AddPNode::Base)->is_top() ||
2110             in(i)->in(AddPNode::Address)->is_top() ||
2111             in(i)->in(AddPNode::Offset)->is_top()) {
2112           doit = false;
2113           break;
2114         }
2115         if (in(i)->in(AddPNode::Offset) != base) {
2116           base = NULL;
2117         }
2118         if (in(i)->in(AddPNode::Offset) != offset) {
2119           offset = NULL;
2120         }
2121         if (in(i)->in(AddPNode::Address) != address) {
2122           address = NULL;
2123         }
2124         // Accumulate type for resulting Phi
2125         base_type = base_type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
2126         address_type = address_type->meet_speculative(in(i)->in(AddPNode::Address)->bottom_type());
2127       }
2128       if (doit && base == NULL) {
2129         // Check for neighboring AddP nodes in a tree.
2130         // If they have a base, use that it.
2131         for (DUIterator_Fast kmax, k = this->fast_outs(kmax); k < kmax; k++) {
2132           Node* u = this->fast_out(k);
2133           if (u->is_AddP()) {
2134             Node* base2 = u->in(AddPNode::Base);
2135             if (base2 != NULL && !base2->is_top()) {
2136               if (base == NULL)
2137                 base = base2;
2138               else if (base != base2)
2139                 { doit = false; break; }
2140             }
2141           }
2142         }
2143       }
2144       if (doit) {
2145         if (base == NULL) {
2146           base = new PhiNode(in(0), base_type, NULL);
2147           for (uint i = 1; i < req(); i++) {
2148             base->init_req(i, in(i)->in(AddPNode::Base));
2149           }
2150           phase->is_IterGVN()->register_new_node_with_optimizer(base);
2151         }
2152         if (address == NULL) {
2153           address = new PhiNode(in(0), address_type, NULL);
2154           for (uint i = 1; i < req(); i++) {
2155             address->init_req(i, in(i)->in(AddPNode::Address));
2156           }
2157           phase->is_IterGVN()->register_new_node_with_optimizer(address);
2158         }
2159         if (offset == NULL) {
2160           offset = new PhiNode(in(0), TypeX_X, NULL);
2161           for (uint i = 1; i < req(); i++) {
2162             offset->init_req(i, in(i)->in(AddPNode::Offset));
2163           }
2164           phase->is_IterGVN()->register_new_node_with_optimizer(offset);
2165         }
2166         return new AddPNode(base, address, offset);
2167       }
2168     }
2169   }
2170 
2171   // Split phis through memory merges, so that the memory merges will go away.
2172   // Piggy-back this transformation on the search for a unique input....
2173   // It will be as if the merged memory is the unique value of the phi.
2174   // (Do not attempt this optimization unless parsing is complete.
2175   // It would make the parser's memory-merge logic sick.)
2176   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)
2177   if (progress == NULL && can_reshape && type() == Type::MEMORY) {
2178     // see if this phi should be sliced
2179     uint merge_width = 0;
2180     bool saw_self = false;
2181     for( uint i=1; i<req(); ++i ) {// For all paths in
2182       Node *ii = in(i);
2183       // TOP inputs should not be counted as safe inputs because if the
2184       // Phi references itself through all other inputs then splitting the
2185       // Phi through memory merges would create dead loop at later stage.
2186       if (ii == top) {
2187         return NULL; // Delay optimization until graph is cleaned.
2188       }
2189       if (ii->is_MergeMem()) {
2190         MergeMemNode* n = ii->as_MergeMem();
2191         merge_width = MAX2(merge_width, n->req());
2192         saw_self = saw_self || phase->eqv(n->base_memory(), this);
2193       }
2194     }
2195 
2196     // This restriction is temporarily necessary to ensure termination:
2197     if (!saw_self && adr_type() == TypePtr::BOTTOM)  merge_width = 0;
2198 
2199     if (merge_width > Compile::AliasIdxRaw) {
2200       // found at least one non-empty MergeMem
2201       const TypePtr* at = adr_type();
2202       if (at != TypePtr::BOTTOM) {
2203         // Patch the existing phi to select an input from the merge:
2204         // Phi:AT1(...MergeMem(m0, m1, m2)...) into
2205         //     Phi:AT1(...m1...)
2206         int alias_idx = phase->C->get_alias_index(at);
2207         for (uint i=1; i<req(); ++i) {
2208           Node *ii = in(i);
2209           if (ii->is_MergeMem()) {
2210             MergeMemNode* n = ii->as_MergeMem();
2211             // compress paths and change unreachable cycles to TOP
2212             // If not, we can update the input infinitely along a MergeMem cycle
2213             // Equivalent code is in MemNode::Ideal_common
2214             Node *m  = phase->transform(n);
2215             if (outcnt() == 0) {  // Above transform() may kill us!
2216               return top;
2217             }
2218             // If transformed to a MergeMem, get the desired slice
2219             // Otherwise the returned node represents memory for every slice
2220             Node *new_mem = (m->is_MergeMem()) ?
2221                              m->as_MergeMem()->memory_at(alias_idx) : m;
2222             // Update input if it is progress over what we have now
2223             if (new_mem != ii) {
2224               set_req(i, new_mem);
2225               progress = this;
2226             }
2227           }
2228         }
2229       } else {
2230         // We know that at least one MergeMem->base_memory() == this
2231         // (saw_self == true). If all other inputs also references this phi
2232         // (directly or through data nodes) - it is dead loop.
2233         bool saw_safe_input = false;
2234         for (uint j = 1; j < req(); ++j) {
2235           Node *n = in(j);
2236           if (n->is_MergeMem() && n->as_MergeMem()->base_memory() == this)
2237             continue;              // skip known cases
2238           if (!is_unsafe_data_reference(n)) {
2239             saw_safe_input = true; // found safe input
2240             break;
2241           }
2242         }
2243         if (!saw_safe_input)
2244           return top; // all inputs reference back to this phi - dead loop
2245 
2246         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
2247         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
2248         PhaseIterGVN *igvn = phase->is_IterGVN();
2249         Node* hook = new Node(1);
2250         PhiNode* new_base = (PhiNode*) clone();
2251         // Must eagerly register phis, since they participate in loops.
2252         if (igvn) {
2253           igvn->register_new_node_with_optimizer(new_base);
2254           hook->add_req(new_base);
2255         }
2256         MergeMemNode* result = MergeMemNode::make(new_base);
2257         for (uint i = 1; i < req(); ++i) {
2258           Node *ii = in(i);
2259           if (ii->is_MergeMem()) {
2260             MergeMemNode* n = ii->as_MergeMem();
2261             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {
2262               // If we have not seen this slice yet, make a phi for it.
2263               bool made_new_phi = false;
2264               if (mms.is_empty()) {
2265                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
2266                 made_new_phi = true;
2267                 if (igvn) {
2268                   igvn->register_new_node_with_optimizer(new_phi);
2269                   hook->add_req(new_phi);
2270                 }
2271                 mms.set_memory(new_phi);
2272               }
2273               Node* phi = mms.memory();
2274               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
2275               phi->set_req(i, mms.memory2());
2276             }
2277           }
2278         }
2279         // Distribute all self-loops.
2280         { // (Extra braces to hide mms.)
2281           for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2282             Node* phi = mms.memory();
2283             for (uint i = 1; i < req(); ++i) {
2284               if (phi->in(i) == this)  phi->set_req(i, phi);
2285             }
2286           }
2287         }
2288         // now transform the new nodes, and return the mergemem
2289         for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2290           Node* phi = mms.memory();
2291           mms.set_memory(phase->transform(phi));
2292         }
2293         if (igvn) { // Unhook.
2294           igvn->hash_delete(hook);
2295           for (uint i = 1; i < hook->req(); i++) {
2296             hook->set_req(i, NULL);
2297           }
2298         }
2299         // Replace self with the result.
2300         return result;
2301       }
2302     }
2303     //
2304     // Other optimizations on the memory chain
2305     //
2306     const TypePtr* at = adr_type();
2307     for( uint i=1; i<req(); ++i ) {// For all paths in
2308       Node *ii = in(i);
2309       Node *new_in = MemNode::optimize_memory_chain(ii, at, NULL, phase);
2310       if (ii != new_in ) {
2311         set_req(i, new_in);
2312         progress = this;
2313       }
2314     }
2315   }
2316 
2317 #ifdef _LP64
2318   // Push DecodeN/DecodeNKlass down through phi.
2319   // The rest of phi graph will transform by split EncodeP node though phis up.
2320   if ((UseCompressedOops || UseCompressedClassPointers) && can_reshape && progress == NULL) {
2321     bool may_push = true;
2322     bool has_decodeN = false;
2323     bool is_decodeN = false;
2324     for (uint i=1; i<req(); ++i) {// For all paths in
2325       Node *ii = in(i);
2326       if (ii->is_DecodeNarrowPtr() && ii->bottom_type() == bottom_type()) {
2327         // Do optimization if a non dead path exist.
2328         if (ii->in(1)->bottom_type() != Type::TOP) {
2329           has_decodeN = true;
2330           is_decodeN = ii->is_DecodeN();
2331         }
2332       } else if (!ii->is_Phi()) {
2333         may_push = false;
2334       }
2335     }
2336 
2337     if (has_decodeN && may_push) {
2338       PhaseIterGVN *igvn = phase->is_IterGVN();
2339       // Make narrow type for new phi.
2340       const Type* narrow_t;
2341       if (is_decodeN) {
2342         narrow_t = TypeNarrowOop::make(this->bottom_type()->is_ptr());
2343       } else {
2344         narrow_t = TypeNarrowKlass::make(this->bottom_type()->is_ptr());
2345       }
2346       PhiNode* new_phi = new PhiNode(r, narrow_t);
2347       uint orig_cnt = req();
2348       for (uint i=1; i<req(); ++i) {// For all paths in
2349         Node *ii = in(i);
2350         Node* new_ii = NULL;
2351         if (ii->is_DecodeNarrowPtr()) {
2352           assert(ii->bottom_type() == bottom_type(), "sanity");
2353           new_ii = ii->in(1);
2354         } else {
2355           assert(ii->is_Phi(), "sanity");
2356           if (ii->as_Phi() == this) {
2357             new_ii = new_phi;
2358           } else {
2359             if (is_decodeN) {
2360               new_ii = new EncodePNode(ii, narrow_t);
2361             } else {
2362               new_ii = new EncodePKlassNode(ii, narrow_t);
2363             }
2364             igvn->register_new_node_with_optimizer(new_ii);
2365           }
2366         }
2367         new_phi->set_req(i, new_ii);
2368       }
2369       igvn->register_new_node_with_optimizer(new_phi, this);
2370       if (is_decodeN) {
2371         progress = new DecodeNNode(new_phi, bottom_type());
2372       } else {
2373         progress = new DecodeNKlassNode(new_phi, bottom_type());
2374       }
2375     }
2376   }
2377 #endif
2378 
2379   return progress;              // Return any progress
2380 }
2381 
2382 //------------------------------is_tripcount-----------------------------------
2383 bool PhiNode::is_tripcount() const {
2384   return (in(0) != NULL && in(0)->is_CountedLoop() &&
2385           in(0)->as_CountedLoop()->phi() == this);
2386 }
2387 
2388 //------------------------------out_RegMask------------------------------------
2389 const RegMask &PhiNode::in_RegMask(uint i) const {
2390   return i ? out_RegMask() : RegMask::Empty;
2391 }
2392 
2393 const RegMask &PhiNode::out_RegMask() const {
2394   uint ideal_reg = _type->ideal_reg();
2395   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );
2396   if( ideal_reg == 0 ) return RegMask::Empty;
2397   assert(ideal_reg != Op_RegFlags, "flags register is not spillable");
2398   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);
2399 }
2400 
2401 #ifndef PRODUCT
2402 void PhiNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2403   // For a PhiNode, the set of related nodes includes all inputs till level 2,
2404   // and all outputs till level 1. In compact mode, inputs till level 1 are
2405   // collected.
2406   this->collect_nodes(in_rel, compact ? 1 : 2, false, false);
2407   this->collect_nodes(out_rel, -1, false, false);
2408 }
2409 
2410 void PhiNode::dump_spec(outputStream *st) const {
2411   TypeNode::dump_spec(st);
2412   if (is_tripcount()) {
2413     st->print(" #tripcount");
2414   }
2415 }
2416 #endif
2417 
2418 
2419 //=============================================================================
2420 const Type* GotoNode::Value(PhaseGVN* phase) const {
2421   // If the input is reachable, then we are executed.
2422   // If the input is not reachable, then we are not executed.
2423   return phase->type(in(0));
2424 }
2425 
2426 Node* GotoNode::Identity(PhaseGVN* phase) {
2427   return in(0);                // Simple copy of incoming control
2428 }
2429 
2430 const RegMask &GotoNode::out_RegMask() const {
2431   return RegMask::Empty;
2432 }
2433 
2434 #ifndef PRODUCT
2435 //-----------------------------related-----------------------------------------
2436 // The related nodes of a GotoNode are all inputs at level 1, as well as the
2437 // outputs at level 1. This is regardless of compact mode.
2438 void GotoNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2439   this->collect_nodes(in_rel, 1, false, false);
2440   this->collect_nodes(out_rel, -1, false, false);
2441 }
2442 #endif
2443 
2444 
2445 //=============================================================================
2446 const RegMask &JumpNode::out_RegMask() const {
2447   return RegMask::Empty;
2448 }
2449 
2450 #ifndef PRODUCT
2451 //-----------------------------related-----------------------------------------
2452 // The related nodes of a JumpNode are all inputs at level 1, as well as the
2453 // outputs at level 2 (to include actual jump targets beyond projection nodes).
2454 // This is regardless of compact mode.
2455 void JumpNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2456   this->collect_nodes(in_rel, 1, false, false);
2457   this->collect_nodes(out_rel, -2, false, false);
2458 }
2459 #endif
2460 
2461 //=============================================================================
2462 const RegMask &JProjNode::out_RegMask() const {
2463   return RegMask::Empty;
2464 }
2465 
2466 //=============================================================================
2467 const RegMask &CProjNode::out_RegMask() const {
2468   return RegMask::Empty;
2469 }
2470 
2471 
2472 
2473 //=============================================================================
2474 
2475 uint PCTableNode::hash() const { return Node::hash() + _size; }
2476 bool PCTableNode::cmp( const Node &n ) const
2477 { return _size == ((PCTableNode&)n)._size; }
2478 
2479 const Type *PCTableNode::bottom_type() const {
2480   const Type** f = TypeTuple::fields(_size);
2481   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2482   return TypeTuple::make(_size, f);
2483 }
2484 
2485 //------------------------------Value------------------------------------------
2486 // Compute the type of the PCTableNode.  If reachable it is a tuple of
2487 // Control, otherwise the table targets are not reachable
2488 const Type* PCTableNode::Value(PhaseGVN* phase) const {
2489   if( phase->type(in(0)) == Type::CONTROL )
2490     return bottom_type();
2491   return Type::TOP;             // All paths dead?  Then so are we
2492 }
2493 
2494 //------------------------------Ideal------------------------------------------
2495 // Return a node which is more "ideal" than the current node.  Strip out
2496 // control copies
2497 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2498   return remove_dead_region(phase, can_reshape) ? this : NULL;
2499 }
2500 
2501 //=============================================================================
2502 uint JumpProjNode::hash() const {
2503   return Node::hash() + _dest_bci;
2504 }
2505 
2506 bool JumpProjNode::cmp( const Node &n ) const {
2507   return ProjNode::cmp(n) &&
2508     _dest_bci == ((JumpProjNode&)n)._dest_bci;
2509 }
2510 
2511 #ifndef PRODUCT
2512 void JumpProjNode::dump_spec(outputStream *st) const {
2513   ProjNode::dump_spec(st);
2514   st->print("@bci %d ",_dest_bci);
2515 }
2516 
2517 void JumpProjNode::dump_compact_spec(outputStream *st) const {
2518   ProjNode::dump_compact_spec(st);
2519   st->print("(%d)%d@%d", _switch_val, _proj_no, _dest_bci);
2520 }
2521 
2522 void JumpProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
2523   // The related nodes of a JumpProjNode are its inputs and outputs at level 1.
2524   this->collect_nodes(in_rel, 1, false, false);
2525   this->collect_nodes(out_rel, -1, false, false);
2526 }
2527 #endif
2528 
2529 //=============================================================================
2530 //------------------------------Value------------------------------------------
2531 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot
2532 // have the default "fall_through_index" path.
2533 const Type* CatchNode::Value(PhaseGVN* phase) const {
2534   // Unreachable?  Then so are all paths from here.
2535   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;
2536   // First assume all paths are reachable
2537   const Type** f = TypeTuple::fields(_size);
2538   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2539   // Identify cases that will always throw an exception
2540   // () rethrow call
2541   // () virtual or interface call with NULL receiver
2542   // () call is a check cast with incompatible arguments
2543   if( in(1)->is_Proj() ) {
2544     Node *i10 = in(1)->in(0);
2545     if( i10->is_Call() ) {
2546       CallNode *call = i10->as_Call();
2547       // Rethrows always throw exceptions, never return
2548       if (call->entry_point() == OptoRuntime::rethrow_stub()) {
2549         f[CatchProjNode::fall_through_index] = Type::TOP;
2550       } else if( call->req() > TypeFunc::Parms ) {
2551         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );
2552         // Check for null receiver to virtual or interface calls
2553         if( call->is_CallDynamicJava() &&
2554             arg0->higher_equal(TypePtr::NULL_PTR) ) {
2555           f[CatchProjNode::fall_through_index] = Type::TOP;
2556         }
2557       } // End of if not a runtime stub
2558     } // End of if have call above me
2559   } // End of slot 1 is not a projection
2560   return TypeTuple::make(_size, f);
2561 }
2562 
2563 //=============================================================================
2564 uint CatchProjNode::hash() const {
2565   return Node::hash() + _handler_bci;
2566 }
2567 
2568 
2569 bool CatchProjNode::cmp( const Node &n ) const {
2570   return ProjNode::cmp(n) &&
2571     _handler_bci == ((CatchProjNode&)n)._handler_bci;
2572 }
2573 
2574 
2575 //------------------------------Identity---------------------------------------
2576 // If only 1 target is possible, choose it if it is the main control
2577 Node* CatchProjNode::Identity(PhaseGVN* phase) {
2578   // If my value is control and no other value is, then treat as ID
2579   const TypeTuple *t = phase->type(in(0))->is_tuple();
2580   if (t->field_at(_con) != Type::CONTROL)  return this;
2581   // If we remove the last CatchProj and elide the Catch/CatchProj, then we
2582   // also remove any exception table entry.  Thus we must know the call
2583   // feeding the Catch will not really throw an exception.  This is ok for
2584   // the main fall-thru control (happens when we know a call can never throw
2585   // an exception) or for "rethrow", because a further optimization will
2586   // yank the rethrow (happens when we inline a function that can throw an
2587   // exception and the caller has no handler).  Not legal, e.g., for passing
2588   // a NULL receiver to a v-call, or passing bad types to a slow-check-cast.
2589   // These cases MUST throw an exception via the runtime system, so the VM
2590   // will be looking for a table entry.
2591   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode
2592   CallNode *call;
2593   if (_con != TypeFunc::Control && // Bail out if not the main control.
2594       !(proj->is_Proj() &&      // AND NOT a rethrow
2595         proj->in(0)->is_Call() &&
2596         (call = proj->in(0)->as_Call()) &&
2597         call->entry_point() == OptoRuntime::rethrow_stub()))
2598     return this;
2599 
2600   // Search for any other path being control
2601   for (uint i = 0; i < t->cnt(); i++) {
2602     if (i != _con && t->field_at(i) == Type::CONTROL)
2603       return this;
2604   }
2605   // Only my path is possible; I am identity on control to the jump
2606   return in(0)->in(0);
2607 }
2608 
2609 
2610 #ifndef PRODUCT
2611 void CatchProjNode::dump_spec(outputStream *st) const {
2612   ProjNode::dump_spec(st);
2613   st->print("@bci %d ",_handler_bci);
2614 }
2615 #endif
2616 
2617 //=============================================================================
2618 //------------------------------Identity---------------------------------------
2619 // Check for CreateEx being Identity.
2620 Node* CreateExNode::Identity(PhaseGVN* phase) {
2621   if( phase->type(in(1)) == Type::TOP ) return in(1);
2622   if( phase->type(in(0)) == Type::TOP ) return in(0);
2623   // We only come from CatchProj, unless the CatchProj goes away.
2624   // If the CatchProj is optimized away, then we just carry the
2625   // exception oop through.
2626   CallNode *call = in(1)->in(0)->as_Call();
2627 
2628   return ( in(0)->is_CatchProj() && in(0)->in(0)->in(1) == in(1) )
2629     ? this
2630     : call->in(TypeFunc::Parms);
2631 }
2632 
2633 //=============================================================================
2634 //------------------------------Value------------------------------------------
2635 // Check for being unreachable.
2636 const Type* NeverBranchNode::Value(PhaseGVN* phase) const {
2637   if (!in(0) || in(0)->is_top()) return Type::TOP;
2638   return bottom_type();
2639 }
2640 
2641 //------------------------------Ideal------------------------------------------
2642 // Check for no longer being part of a loop
2643 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2644   if (can_reshape && !in(0)->is_Loop()) {
2645     // Dead code elimination can sometimes delete this projection so
2646     // if it's not there, there's nothing to do.
2647     Node* fallthru = proj_out_or_null(0);
2648     if (fallthru != NULL) {
2649       phase->is_IterGVN()->replace_node(fallthru, in(0));
2650     }
2651     return phase->C->top();
2652   }
2653   return NULL;
2654 }
2655 
2656 #ifndef PRODUCT
2657 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {
2658   st->print("%s", Name());
2659 }
2660 #endif